Access Management in the Vicinity of Intersections

Technical Summary

Access Management in

the Vicinity of Intersections

FHWA-SA-10-002

Foreword

This technical summary is designed as a reference for State and local transportation oﬃcials, Federal Highway

Administration (FHWA) Division Safety Engineers, and other professionals involved in the design, selection,

and implementation of access management near traditional intersections (e.g., signalized, unsignalized and

stop controlled intersections). Its purpose is to provide an overview of safety considerations in the design,

implementation, and management of driveways near traditional intersections in urban, suburban, and rural

environments where design considerations can vary as a function of land uses, travel speeds, volumes of traﬃc

by mode (e.g., car, pedestrian, or bicycle), and many other variables.

The technical summary does not include any discussion on roundabout intersections. More information

about roundabouts is available in Roundabouts: An Informational Guide, published by the FHWA [1]. Section 1

of this technical summary presents an overview of access management factors that should be considered for

improving safety near intersections in any setting. Section 2 presents access management considerations and

treatments to improve safety near traditional intersections in suburban, urban, and rural settings. This section

features a case study of an access management retroﬁt project in a suburban area. Section 3 points the reader to

additional resources.

This publication does not supersede any publication; and is a Final version.

Disclaimer and Quality Assurance Statement

Notice

This document is disseminated under the sponsorship of the U.S. Department

of Transportation in the interest of information exchange. The U.S. Government

assumes no liability for the use of the information contained in this document.

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high-quality information

to serve Government, industry, and the public in a manner that promotes

public understanding. Standards and policies are used to ensure and maximize

the quality, objectivity, utility, and integrity of its information. FHWA periodically

reviews quality issues and adjusts its programs and processes to ensure

continuous quality improvement.

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Contents

Introduction 1.

Section 1: General.Access.Management

Considerations. 2.

1.1 Locate Driveways on the Appropriate

Roadway Functional Classiﬁcation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.2 Limiting Driveways within the Functional Area

of an Intersection Improves Safety. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.3 Reducing the Number and Types of Conﬂict Points

Created by a Driveway May Reduce Crashes . . . . . . . . . . . . . . . . . . . . . . . . 3

1.4 Eliminating Left-Turn Movements at Driveways

is Beneﬁcial from a Safety Perspective . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.5 Median Treatments Can Impact Safety . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.6 Reducing Driveway Density Reduces Crash Rates. . . . . . . . . . . . . . . . . . . . 5

1.7 Properly Designed Driveways Inﬂuence Safety

and Mobility at the Driveway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Section 2: Special.Considerations.for.Suburban,

Urban.and.Rural.Areas. 7.

2.1. Access Management Considerations

in the Vicinity of Suburban Intersections . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.2 Access Management Considerations

in the Vicinity of Urban Intersections . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

2.3 Access Management Considerations

in the Vicinity of Rural Intersections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Section 3: References. 14.

Cover Photo by Ralph Bentley

FHWA | Access Management in the Vicinity of Intersections iii

FHWA | Access Management in the Vicinity of Intersections iv

Introduction

“Access management” refers to the design, implementation and management of entry and exit

points (i.e., driveways, entrances or exits) between roadways and adjacent properties. These entry

and exit points can be managed by careful planning regarding their location, the types of turning

movements allowed, and if appropriate, medians that provide or prohibit access to the driveways.

Developing and implementing eﬀective access management strategies that promote or improve

safety requires considering the location of driveways in the context of current and future access

needs, current and future intersection operations, and mobility for pedestrians and bicyclists.

This technical summary is designed as a reference for

State and local transportation oﬃcials, Federal Highway

Administration (FHWA) Division Safety Engineers, and

other professionals involved in the design, selection, and

implementation of access management near traditional

intersections (e.g., signalized, unsignalized and stop-

controlled intersections). Its purpose is to provide

an overview of safety considerations in the design,

implementation, and management of driveways near

traditional intersections in urban, suburban, and rural

environments where design considerations can vary as a

function of land uses, travel speeds, volumes of traﬃc by

mode (e.g., car, pedestrian, or bicycle), and many other

variables. The technical summary does not include any

discussion on roundabout intersections. More information

about roundabouts is available in Roundabouts: An

Informational Guide, published by the FHWA [1].

Section 1 of this technical summary presents an overview

of access management factors that should be considered

for improving safety near intersections in any setting.

Section 2 presents access management considerations

and treatments to improve safety near traditional

intersections in suburban, urban, and rural settings. This

section features a case study of an access management

retroﬁt project in a suburban area. Section 3 provides

references.

Photo: Ralph Bentley (used with permission)

FHWA | Access Management in the Vicinity of Intersections 1

2 FHWA | Access Management in the Vicinity of Intersections

Providing access (i.e., driveways, entrances or exits) onto

roadways with the lowest traﬃc volumes and speeds

generally improves safety near intersections. In planning,

designing, and managing access, critical consideration

must be given to arterial and collector streets as these

streets serve both mobility and access functions. To the

extent possible, it is best to manage driveways so that

access is provided to and from the roadway with the

lower functional classiﬁcation as these roadways typically

have lower traﬃc volumes and speeds. This helps to

reduce the frequency of conﬂicts, which minimizes both

the opportunity for crashes and the severity of those

crashes, should they occur.

Section 1: General Access Management Considerations

Planning, designing, and implementing access management strategies to promote safety near inter-

sections begins with an awareness of several considerations. These considerations are independent

of the environment or setting in which the driveway is located (i.e., urban, suburban, or rural). These

factors include roadway functional classiﬁcation (sometimes referred to as “roadway hierarchy”

1

);

the functional area of the intersection; the location and number of driveways and resulting conﬂict

points; the use of medians; and driveway design.

By considering the following seven guidelines when developing and evaluating access management

treatments, practitioners can apply access management techniques to help improve safety in the

vicinity of intersections

2

.

UPSTREAM

DOWNSTREAM

UPSTREAM

Physical Area of Intersection

Functional Area of Intersection

Figure 1: Functional and Physical Areas of an Intersection

1 Typical roadway functional classiﬁcations include freeway, arterial, collector, and local street—with freeways providing the highest level of

mobility but the lowest level of accessibility, and local streets providing the highest level of accessibility but lowest level of mobility (assuming

normal traﬃc).

2 These are general guidelines and may not apply to all situations. Understanding these principles can help practitioners more comprehensively

evaluate options, understand tradeoﬀs, and make better decisions to help promote the safest possible access management treatments in the

vicinity of intersections.

1.2 Limiting Driveways within the Functional Area of an Intersection Improves Safety

Figure 1 provides a schematic

representation of functional and physical

areas of an intersection. The physical

area of an intersection is a ﬁxed area that

represents the space conﬁned within the

corners of the intersection.

The functional area of an intersection

includes areas upstream and downstream

of the intersection. Unlike the physical

area of an intersection, the functional

area of an intersection is variable. The

American Association of State Highway

and Transportation Oﬃcials’ (AASHTO) A

Policy On Geometric Design of Highways and

Streets [2] deﬁnes the upstream functional

1.1 Locate Driveways on the Appropriate Roadway Functional Classiﬁcation

area of an intersection as a variable distance, inﬂuenced

by: 1) distance traveled during perception-reaction time,

2) deceleration distance while the driver maneuvers to a

stop, and 3) the amount of queuing at the intersection

3

.

The upstream functional area is highly dependent on

whether or not the traﬃc in the through lane is required

to come to a stop at the intersection. Therefore, the

functional area should be a consideration in situations

where a driveway is near an intersection (due to a traﬃc

signal or stop sign).

For example, at a stop-controlled intersection with

approach speeds of 30 mph and a queue length of

125 feet (with additional assumptions for perception-

reaction time and deceleration distance), the upstream

functional area of the intersection is 200 feet. For a

signalized intersection with identical speed and queue

characteristics, the upstream functional area is 395 feet.

At that same stop-controlled intersection with a similar

queue but a higher approach speed – 50 mph – the

upstream functional area is 425 feet (compared to

just 200 feet with 30 mph approach speeds). For a

signalized intersection with identical speed and queue

characteristics, the upstream functional area is 735

feet [3].

The AASHTO Policy on Geometric Design does not deﬁne

the downstream functional area of the intersection as the

criteria used to determine the downstream functional

area can vary between jurisdictions. The Access

Management Manual [3], published by the Transportation

Research Board (TRB), notes that “stopping sight

distance is one method for establishing the downstream

functional distance of an intersection.”

In the case of the stop-controlled intersection

previously described (30 mph approach speed, 125

feet queue), the downstream functional area using the

Access Management Manual’s stopping sight distance

calculation is 200 feet. At an approach speed of 50

mph the downstream functional area is 425 feet. When

calculating downstream functional area with this method,

traﬃc control at the intersection is not a factor.

Limiting or, where possible, eliminating driveways within

the functional area of an intersection (upstream and

downstream) helps reduce the number of decisions

motorists must make while traveling through an

intersection and improves safety in the vicinity of an

intersection. A recent study evaluating crashes in the

vicinity of signalized intersections in suburban areas

completed by the Utah Department of Transportation [4]

provides one illustration of the correlation between

driveways in the functional area of intersections and

increased safety risk. The study evaluated right-turn and

rear-end crashes at signalized intersections in suburban

areas. The study found that the existence of accesses

within the upstream functional area of the intersection

correlated to increased crashes and crash severity costs.

The report identiﬁed an even greater increase in total

crashes, crash rates, and rear-end crashes as commercial

access density increased

4

.

Additionally, a recent study by the Texas Transportation

Institute (TTI), the “Roadway Safety Design Synthesis” [5]

discusses the safety eﬀect of driveways in rural areas.

The study includes equations to calculate the Accident

Modiﬁcation Factor (AMF) for access control based

on the number of driveways within 250 feet of a rural

intersection.

1.3 Reducing the Number and Types of Conﬂict Points Created by a Driveway May

Reduce Crashes

In general, the number and types of conﬂict points

(i.e., the number of locations where the travel paths

of two diﬀerent vehicles may cross) at the intersection

of a driveway and a public road inﬂuence the safety

of motorists. It is desirable to minimize the number

of conﬂict points created with existing and future

driveways since more conﬂict points increase the risk of

a crash occurring. For example, a crash due to crossing

maneuvers (created by motorists turning across the

roadway or making left turns) can lead to more severe

crashes then merging or diverging conﬂicts because of

the angle and speed diﬀerentials between the vehicles.

As the angle and speed diﬀerentials increases, crash

severity can also increase.

The number and type of conﬂict points at a driveway

can be managed by limiting both the amount of access

allowed at the driveway (e.g., full-movement, left-in/left-

out, right-in/right-out, right-in only or right-out only) and

3 American Association of State Highway and Transportation Oﬃcials, A Policy On Geometric Design of Highways and Streets, 5th Edition

(Washington, DC: 2004).

4 This study examined safety-related data upstream of signalized intersections within suburban areas.

FHWA | Access Management in the Vicinity of Intersections 3

the location of the driveway relative to other driveways in

the area. In most cases, property owners prefer to have

at least one direct, full-movement driveway from their

property onto the major street (i.e., the street with higher

traﬃc volumes) adjacent to the property. In many cases,

it may occur that property owners are requesting direct,

full-movement driveways to diﬀerent properties on both

sides of the major street. It is not always possible to

align these driveways to minimize the number of conﬂict

points, so another strategy, such as implementation of a

raised median, should be considered (see Section 1.5 for

information on median treatments).

Figure 2 illustrates a scenario in which it is not possible

to align the full-movement driveways in a manner that

would reduce conﬂict points. Figure 3 illustrates how

construction of a raised median on the major roadway

could reduce the number of conﬂict points in this

situation. The raised median in Figure 3 limits the access

to Driveways A and B to right-in/right-out movements

only. Also, the number of conﬂicts in the vicinity of

Driveways C and D in Figure 2 are reduced by relocating

Driveway C to the minor road (see Figure 3). This solution

limits conﬂict points by providing a direct, full-movement

driveway (i.e., left-in/left-out/right-in/right-out) to the

minor road, and by constructing a median on the major

road and limiting access at Driveway D to right-in/right-

out only.

Finally, in Figure 3, additional right-in/right-out only

driveways are provided on the minor street (Driveways E

and F) to improve the access to the properties adjacent to

Driveways B and D. If possible, it is preferable to provide

driveways onto the minor street instead of on the major

street in order to preserve mobility on the major street.

Limiting turn movements to properties adjacent to the

roadway can result in circuitous travel to and from a site.

For example, a motorist exiting Driveway B is limited to

one direction of travel and is required to make a U-turn or

use Driveway F to reach other destinations.

MAJOR

ROADWAY

MINOR

ROADWAY

B D

A

C

Figure 2: Typical Access Scenario at the Intersection of Two Public Roadways

MAJOR

ROADWAY

MINOR

ROADWAY

B D

A

C

EF

Figure 3: Desirable Access Scenario at the Intersection of Two Public Roadways

1.4 Eliminating Left-Turn Movements at Driveways is Beneﬁcial from a Safety Perspective

Where restricting turning movements to and from a

driveway is possible, it is most beneﬁcial from a safety

perspective to prohibit left-turning movements. Research

suggests that approximately 72 percent of crashes at a

driveway involve a left-turning vehicle [6]. As illustrated

in Figure 4, approximately 34 percent of these crashes

are due to an outbound vehicle turning left across

through traﬃc. Twenty-eight percent of crashes are

due to an inbound, left-turning vehicle conﬂicting with

opposite direction through traﬃc, and 10 percent are

FHWA | Access Management in the Vicinity of Intersections 4

due to outbound, left-turning movements

incorrectly merging into the same direction

through movement. This suggests that

reducing or eliminating left turns to or from

driveways, combined with eﬀorts to reduce

conﬂict points (described in Section 1.3),

enhances safety. When turn movements

are restricted at driveways, roadway

engineers, planners, and policy makers

need to consider the tradeoﬀs of shifting

the turning movement to another location

along the roadway.

1.5 Median Treatments Can Impact Safety

One method to manage or limit left turns to and from

driveways is with the proper use of medians. Proper use

of medians has been found to improve roadway safety

signiﬁcantly relative to undivided roadways. National

Cooperative Highway Research Program (NCHRP)

Report 420: Impacts of Access Management Techniques [7]

identiﬁes two types of medians typically used:

• Non-traversable medians.

• Continuous two-way left-turn lanes (TWLTL).

Non-traversable medians separate opposing

directions of travel, signiﬁcantly reducing the potential

for head-on crashes and physically eliminating or limiting

where left-turns and crossing movements across the

median can occur. When a non-traversable median of

suﬃcient width is constructed, it can also provide refuge

28% 34% 10%

Figure 4: Crash Percentages for Turning Motorists to and from the Driveway

for pedestrians crossing the roadway. Non-traversable

medians generally result in an overall crash reduction

of approximately 35 percent as compared to undivided

roadways.

TWLTLs provide for left turns in both directions of travel,

except near signalized intersections where the center turn

lane transitions to a conventional left-turn lane for one

direction of travel. TWLTLs generally result in an overall

crash reduction of approximately 33 percent as compared

to undivided roadways. However, NCHRP Report 420

states that “Most studies, and the models derived from

them, also suggest that safety is improved where physical

medians replace TWLTLs.” Factors to consider include

diﬀering roadway types, traﬃc volumes, travel speed,

number of through lanes, and the number of left turns

and crossing maneuvers.

1.6 Reducing Driveway Density Reduces Crash Rates

Research over the past decades has

consistently shown that crash rates

increase as driveway density increases

on a roadway (i.e., number of driveways

per mile). Figure 5 illustrates this trend

under a variety of roadway conditions and

environments across the U.S. and in Canada.

Property access points should be designed,

approved, and permitted within the context

of the number of driveways on both sides

of the street within the vicinity of the

proposed access points and should not be

considered in isolation. Possible strategies

10

8

6

4

2

0

Crashes / Million Vehicle Miles Traveled

1

2

8

7

3

4

5

6

9

1

British Columbia 2-Lane Urban

2

Michigan 2-Lane Urban

3

Michigan 2-Lane Rural

4

British Columbia 4-Lane Urban

5

Florida*

6

Florida*

7

Florida*

8

Oregon Urban*

9

Oregon Rural*

0

10

20 30 40 50 60 70 80 90

Access Points / Mile

* Road type not specified

Figure 5: Eﬀect of Access Point Density on Crash Rate

FHWA | Access Management in the Vicinity of Intersections 5

to reduce the number of driveways over time include the

use of shared access to serve more than one property,

the planning and development of additional roadways to

provide connectivity and complementary mixed uses to

minimize the need for multiple parking areas, and multiple

driveways.

1.7 Properly Designed Driveways Inﬂuence Safety and Mobility at the Driveway

Driveway connections to public roads must be

adequately designed to ensure safe and eﬃcient

movement of vehicles to and from the roadway,

balancing safety with mobility interests. There are

many elements to consider in proper driveway design,

including upstream and downstream sight distance, the

angle at which the driveway intersects the major road,

the appropriate width of the driveway in tandem with

curb radii so that vehicles can make the desired turn

movement, the number of lanes (suﬃcient for the volume

at the site), and the vertical grade and length of the

driveway throat.

In general, driveways should be of suﬃcient length to

allow motorists to completely pull oﬀ the road without

interference from on-site parked vehicles, vehicle queues,

or pedestrian or vehicle circulation once they enter

the property adjacent to the roadway. The design of

a driveway at any given location is a function of the

design vehicle, travel speeds onto and oﬀ of the property,

traﬃc volume, pedestrian and bicycle volume, and the

type of traﬃc control (e.g., a signalized driveway should

accommodate queues that may conﬂict with on-site

turning movements). For motorists leaving a property, the

vertical alignment of the driveway should be as close to

level as possible where it intersects with the roadway. The

driveway should be level for a suﬃcient distance to allow

the motorist to easily stop with an unobstructed view

upstream and downstream prior to entering the major

roadway.

The Florida Department of Transportation (FDOT)

Driveway Manual [8] provides a thorough overview of

the criteria and application methods that a practitioner

should consider in the design of a driveway. In addition,

jurisdiction-speciﬁc design guidelines should be

consulted when designing a driveway.

Photo: Ralph Bentley (used with permission)

FHWA | Access Management in the Vicinity of Intersections 6

Section 2: Special Considerations for Suburban, Urban

and Rural Areas

Urban, suburban, and rural areas each present unique opportunities and challenges with respect

to design, selection and implementation of access management strategies that provide the high-

est level of safety in the vicinity of intersections. The following sections (2.1, 2.2 and 2.3) provide an

overview of some additional special considerations that apply within each of these environments.

Because suburban areas oﬀer the greatest opportunities to improve safety through access manage-

ment strategies (due to development trends and traﬃc volumes), this discussion addresses suburban

areas ﬁrst, followed by a discussion of urban and rural environments.

2.1 Access Management Considerations in

the Vicinity of Suburban Intersections

Suburban areas oﬀer the greatest opportunity to

positively impact safety through access management

treatments for several reasons. New development

and redevelopment often occurs on large parcels

of land, providing planners with more ﬂexibility and

options for implementing optimal access management

treatments. This can provide the opportunity for access

to be considered from a systematic perspective, from

the outset of a project, where stakeholders have the

opportunity to plan for the appropriate number of

driveways and optimum types of access (e.g., right-in/

right-out only; or right-in/right-out-left-in). For example,

access to developments on corner lots may be limited

to a side street where traﬃc volumes and speeds are

typically lower. Where access to a major roadway is

allowed, agencies with authority over the roadways have

opportunities to limit turn movements to and from the

driveway with physical treatments, such as medians along

the major roadway and/or median islands at locations

where the driveway connects to the major roadway.

Further, adjacent land uses, including residential,

commercial, and industrial require signiﬁcant access

management planning and accommodation. Finally,

while suburban areas are often lower density than urban

areas, their residential and commercial centers are often

connected by higher speed arterials (35 to 50 mph and

occasionally up to 55 mph) than are found in urban areas,

creating safety risks and opportunities through access

management planning and implementation.

This section describes speciﬁc characteristics and access

management challenges and opportunities associated

with suburban areas and intersections, and provides a

summary of potential access management treatments

that can improve safety for motorists, bicyclists, and

pedestrians. It also features a case study highlighting an

access management retroﬁt project in a suburban area.

2.1.1 Characteristics of Suburban Roads and Intersections

As the distance from the urban core increases, the density

of development decreases. Emphasis on residential

land use grows as one moves further from the urban

core. Suburban areas tend to be characterized by large-

scale and residential, commercial, industrial, or retail

development typically separated by larger distances than

in the urban core. In developing suburban areas, parcels

can be combined to accommodate larger developments,

such as big box retail and strip malls. Land values often

rely on spacious parking lots and convenient access to

adjacent roadways.

Physical characteristics of suburban areas include medium

to long block lengths that may vary from 400 feet to a

half mile and signalized intersections on arterials and

major collectors. Traﬃc characteristics of suburban areas

include roadways with speeds that generally range from

35 to 50 mph (and occasionally up to 55 mph), medium

to high traﬃc volumes (30,000 to 50,000 vehicles per day)

on mainline roadways; and 5,000 to 15,000 vehicles per

day on side streets and non-residential driveways. Physical

characteristics include:

• Moderate to large site setbacks for structures.

• Non-traversable medians (in some cases) or continuous

two-way left-turn lanes (TWLTLs) .

• Left- and right-turn lanes.

• Six or fewer traﬃc signals per mile.

FHWA | Access Management in the Vicinity of Intersections 7

Table 1

R

eported Crashes on OR 82 at

Study Driveway (November 1994 to August 1997)

Total

Crashes

Crash Severity

Fatality Injury PDO Left-turn

12 0 6 6 12

PDO = Property Damage Only

Figure A: Original Driveway and Roadway Conﬁguration

Suburban Case Study: La Grande, Oregon

In June 1996, the Oregon Department of Transportation

(ODOT) initiated a study of an unsignalized, full-access

driveway (i.e., left and right turns allowed for inbound and

outbound vehicles) in a suburban area. The study driveway

was located on Oregon 82 (OR 82), approximately 600 feet

south of Walton Road in La Grande, Oregon. La Grande

has a population of approximately 12,500, and OR 82 is an

undivided ﬁve-lane road. Adjacent land use development

is a mix of big-box retail, commercial, and some industrial

uses. The posted speed on this segment of OR 82 is 40

mph. During a 34-month period

5

between November 1994

and August 1997, ODOT crash reports show that 12 crashes

occurred at this unsignalized driveway. Figure A depicts

this driveway (driveway “A”) and the roadway conﬁguration

during the study period, prior to implementation of any

access management treatments.

All of these crashes included a collision with a vehicle

moving northbound on OR 82. One of the crashes involved

a motorist turning left out of driveway “A” onto southbound

OR 82 and colliding with a motorist traveling northbound

on OR 82, who was turning right into the driveway.

After performing a review of the roadway conﬁguration,

ODOT staﬀ recommended the following access

management improvements, depicted in Figure B:

• Restrict left turns to and from the driveway with a

non-traversable median to eliminate left turns into

and out of the site.

• Modify the adjacent signalized intersection to

accommodate U-turns to allow motorists to access

southbound OR 82, which has been eliminated at the

During the study period, the average annual daily traﬃc

volumes on OR 82 approached 17,200 in the vicinity of

driveway “A.” Data also showed that approximately 500

vehicles per day traveled inbound/outbound on the study

driveway “A.” The average crash rate was 0.66 crashes per

million entering vehicles

6

.

Table 1 summarizes the crashes

reported during this period.

driveway with the non-traversable median.

• Construct a northbound right-turn deceleration lane

in advance of driveway “A.” This treatment reduces

the speed diﬀerential between motorists slowing

to access the driveway and following motorists,

while improving sight distance upstream from the

driveway.

The proposed access management treatments were

approved and funded through the State’s access

management fund. The State implemented the

recommended improvements in August 1997.

RIGHT-TURN LA NE

Figure B: OR 82 Roadway Conﬁguration After Implementation of

Access Management Techniques

In the ten years following implementation, only two crashes

have occurred at the unsignalized driveway on OR 82 and

neither involved another vehicle

7

.

Given the estimated

18,900 vehicles per day on OR 82 for the 10-year period

after the access management treatments were made,

8

this

equates

to

a

crash

rate

of

approximately

0.06

.

All

reported

crashes

involved

left-turning

vehicles.

Eleven

of

the crashes involved vehicles turning left from the driveway

onto southbound OR 82.

5 The 34-month study period represents the time period from when the full access driveway was approved until when ODOT completed mitigation measures.

6 Crash rate is calculated by: 1) multiplying average daily traﬃc by the number of years of crash data by 365 days per year, and dividing by 1,000,000 and 2)

dividing the total number of crashes at the site during the study period by the million entering vehicles calculated in Step 1.

7 One crash involved a single vehicle and a ﬁxed object, and the other involved a vehicle attempting a left turn across the raised median.

8 Based on a review of ODOT crash reports for the 10-year period from September 1, 1997, through August 31, 2007.

FHWA | Access Management in the Vicinity of Intersections 8

A

X

A

X

Traﬃc signal spacing in suburban areas is a function of adequate progression of traﬃc on the mainline roadway.

Roadway and intersection improvement projects often

are required to provide additional capacity for increasing

traﬃc volumes.

the ability to progress two-way traﬃc along the mainline

roadway. Signalized driveways are often not permitted in

private developments but may be allowed if the spacing

and timing can meet established standards to ensure

2.1.2 Potential Access Management Treatments to Improve Safety for Motorists in Suburban Areas

The following access management

techniques can help to improve motorist

safety and mobility at access points

implemented in the vicinity of suburban

intersections:

• Locate driveways upstream of the vehicle

queue caused when the downstream

traﬃc signal is red. Figure 6 illustrates

this scenario, in which site driveway

“A” is located beyond the limits of the

typical queue as shown with the yellow

(light) vehicles, with current traﬃc

volumes. Without changes in capacity,

existing traﬃc queues will grow as traﬃc

volumes increase. If possible, therefore,

as development occurs, plan and

locate driveways for future estimated

traﬃc volumes. Figure 7 demonstrates

potential access issues at driveway “A”

if future traﬃc queuing conditions, as

illustrated with the blue (dark) vehicles,

are not anticipated.

• Prohibit median openings to restrict

driveway movements to and from the

left-turn lane at a major intersection.

Figure 8 illustrates the risks of allowing

such a median opening. In this

example, motorists turning left into the

site access may conﬂict with the left-

turning or through traﬃc.

• In cases where there is a traversable

median (e.g., TWLTL), aligning

driveways to have a positive oﬀset to

minimize conﬂicts between left-turning

vehicles is advantageous. Figure 9

Figure 6: Driveway Location in Relation to

Traﬃc Queues on a Major Roadway

illustrates driveway alignment with a positive oﬀset. With

a positive oﬀset, motorists can use the two-way, left-turn

lane to access either driveway with a reduced likelihood

of a crash. Figure 10 demonstrates a negative oﬀset

of driveway. In Figure 10 if two motorists are using the

two-way, left-turn lane at the same time, the drivers’ paths

Figure 8: Avoid Median Opening Across Left-Turn Lane for Downstream Intersections (Courtesy of FDOT)

Figure 7: Driveway Location in Relation to

Future Traffic Queues on a Major Roadway (Blue

Vehicles with X Indicate Future Traffic Queues)

would overlap (i.e., a crash may occur) as each driver tries to

access the driveways.

• Where it is not possible to align driveways with a positive

oﬀset (as depicted in Figure 10), align driveways directly

across the street from one another. Figure 11 illustrates this

technique, which allows drivers to access either driveway

without utilizing the same median area while decelerating

prior to turning from the major roadway.

FHWA | Access Management in the Vicinity of Intersections 9

Figure 9: Locate Driveways on Opposite Sides of Figure 10: Avoid Locating Driveways on Opposite

Sides of the Roadway that Create an Overlap for

Left Turns Exiting the Major Roadway

Figure 11: Align Driveways on Opposite Sides of

a Roadway to Achieve a Positive Oﬀset the Roadway

2.1.3 Potential Access Management Treatments to Improve Safety for Bicyclists and Pedestrians in

Suburban Areas

The following access management approaches can

help to improve pedestrian and bicyclist safety as well

as mobility at access points in the vicinity of urban

and suburban intersections (both signalized and

unsignalized):

• Provide raised medians on the major roadway to prohibit

vehicles from turning left into driveways. This improves

pedestrian safety by reducing the number of potential

pedestrian-vehicle conﬂicts at a driveway.

• Construct a channelized island between the inbound and

outbound movements at right-turn-only driveways to

provide a pedestrian refuge across the driveway.

• Minimize the width of the driveway as much as possible in

order to reduce pedestrian crossing distances (i.e., reduce

exposure).

• Place sidewalks and pedestrian driveway crossings so that

pedestrians are visible to the drivers, and drivers are visible

to the pedestrians. Do not block pedestrian-driver sight-

lines with landscaping or signage.

• Include bike lanes and signage, as appropriate, to alert

bicyclists that motorists may be entering or exiting a

driveway and to alert motorists that bicyclists may be

crossing the driveway.

2.2 Access Management Considerations in the Vicinity of Urban Intersections

Implementing access management treatments in urban

areas can be diﬃcult to achieve because of some of

the constraints in urban areas and the amount of time

planning and implementation can consume for local

jurisdictions. This section describes speciﬁc characteristics

and design challenges associated with access

2.2.1 Characteristics of Urban Roads and Intersections

Urban areas (including central business districts) are

typically characterized by dense, multi-modal, fully

built-out transportation systems. Adjacent land uses

are typically high-density oﬃce, commercial, and

management near urban intersections (Section 2.2.1), and

provides a summary of potential access management

treatments that can improve the safety for motorists

(Section 2.2.2), bicyclists, and pedestrians (Section 2.2.3).

retail developments with minimal setbacks from the

street. Parking is usually along roadways, in parking

structures, and in some cases available via surface parking

lots. Older businesses often rely on on-site parking;

FHWA | Access Management in the Vicinity of Intersections 10

therefore, eliminating driveways on these properties can

signiﬁcantly impact business operations.

Physical characteristics of urban environments include

short block lengths (200 to 350 feet), two-way streets with

some left-turn lanes, six or more traﬃc signals per mile,

and minimal site setbacks. Where there are driveways

to and from the streets, the driveways have small radii

and width, and curbs and gutters exist in almost all areas.

Intersections are controlled with a mix of signalized

or unsignalized intersections while the driveways are

generally unsignalized.

Traﬃc characteristics include low to medium driveway

volumes (500 to 5,000 vehicles per day), medium to high

adjacent street traﬃc volumes (20,000 to 50,000 vehicles

per day), and coordinated, ﬁxed signal timing. Pedestrians,

bicycles, and buses often are present, and speeds

generally are equal to or below 30 mph.

One-way couplets are often found within the urban area

and provide access management beneﬁts. One-way

streets limit driveways to right-in/right-out only or left-in/

left-out only turning maneuvers and reduce the number

of crossing conﬂict points and the spacing required

between adjacent driveways. One-way streets also reduce

the need for intersection sight distance downstream of a

driveway as there is no oncoming vehicular traﬃc.

One-way streets can also be beneﬁcial for pedestrians

crossing the street as they only need to look for

oncoming traﬃc in one direction.

Based on a speed of 30 mph, the upstream functional

area of an urban signalized intersection often exceeds the

length of a typical urban block. For this reason, engineers

in urban areas often cannot avoid placing driveways

within functional areas of intersections. Furthermore,

on-street parking and other sources of friction within

an intersection’s functional area, including bus pull-outs

and areas for truck loading/unloading, can diminish the

beneﬁts otherwise associated with placing driveways

outside of the functional area of an intersection.

2.2.2 Potential Access Management Treatments to Improve Motorist Safety Near

Urban Intersections

The following access management approaches can help to

improve motorist safety and mobility at access points implemented

in the vicinity of urban area intersections. The techniques apply

whether or not the urban intersection is signalized:

• Develop a right-turn lane for inbound vehicles on the through road

in advance of the site driveway by removing a section of on-street

parking; this removes the turning vehicle from the ﬂow of traﬃc.

• Avoid locating on-site parking bays near site driveways. This allows

motorists to drive completely onto the property without having to

stop for other motorists completing on-site parking maneuvers, as

illustrated in Figure 12. Parking maneuvers near the site driveway

can also result in delays for inbound motorists, creating queues

that extend back into the major roadway. Figure 13 illustrates an

unobstructed driveway, which allows motorists to exit the roadway

unimpeded by other motorists maneuvering in the driveway.

• Replace gated parking entries with alternate ticketing options to

decrease the driver’s entrance time into the driveway and oﬀ the main

roadway, thus reducing the likelihood of queues on the main roadway.

• Locate loading and bus bays on the far side of the driveway to

maximize sight distance for motorists exiting a driveway.

• Place driveways on lower volume roadways (side streets or alleys)

wherever possible (Figure 3).

Figure 12: Parking Maneuvers Close to the Roadway

Result in Delays for the Inbound Motorist

Figure 13: Unobstructed and Clearly Deﬁned

Driveways Allow Easy Access for Inbound Motorists

FHWA | Access Management in the Vicinity of Intersections 11

• Sign and stripe for right-turn, outbound movements

only, wherever possible. It is not always possible to

enforce this condition without geometric restrictions

(i.e., raised channelization) to eliminate outbound, left-

turning conflicts.

• Place driveways that serve left-turning, inbound vehicles

near the center of the block to minimize interaction with

upstream and downstream intersection queues, thus

reducing the potential for left-turn related crashes.

• Place driveways on one-way streets where possible. This

results in right-in/right-out only or left-in/left-out only

driveways and therefore fewer conﬂict points.

• Position driveways as far upstream from intersections

as possible to provide motorists leaving a property with

distance along the roadway to make any necessary

lane changes for traveling through the downstream

intersection (e.g., maneuvering into an intersection left-

or right-turn lane).

2.2.3 Potential Access Management Treatments to Improve Safety for Pedestrians and Bicyclists in Urban

Areas.

In addition to the access management treatments

identiﬁed in 2.1.3, the following access management

approaches can help to improve pedestrian and bicyclist

safety and mobility at access points in the vicinity of

urban intersections. The techniques apply whether or not

the urban intersection is signalized:

• Use colored pavement across driveways in combination

with crosswalk markings, and audio/visual treatments for

exiting vehicles with limited sight distance. Such treatments

include a signal and/or ﬂashing sign that is activated to alert

pedestrians a vehicle is about to cross the sidewalk from an

adjacent parking area.

• Restrict inbound vehicle speeds by designing the driveway

access with appropriately designed radii.

• Smaller driveway radii of 25 to 35 feet are more sensitive to

pedestrian movements [5] because motorists have to slow

down to complete the turn. However, on-street parking and

bike lanes can increase the eﬀective driveway radius, so care

should be taken to balance vehicle and pedestrian safety.

2.3 Access Management Considerations in the Vicinity of Rural Intersections

Rural areas, in general, have fewer access management

needs in the vicinity of rural intersections than urban

or suburban areas. Intersections with county roads are

generally infrequent, and these roads often have fairly

low traﬃc volumes. The majority of driveways in the

vicinity of intersections serve low traﬃc generators such

as single family homes and/or farms. Large property

frontages adjacent to the roadway allow the regulating

jurisdiction to locate a driveway a signiﬁcant distance

from the intersection. However, rural intersections can

2.3.1 Characteristics of Rural Roads and Intersections

Rural areas are characterized by low-density commercial

development, such as gas stations and small convenience

stores, industrial land and farm land, as well as, in some

cases, large expanses of private or publicly-owned

undeveloped property. Large property frontages along

rural roadways allow jurisdictions to adequately space

driveways, though topographical and environmental

constraints (e.g., steep hills, wetlands, or rivers) may

impact where driveways can be located.

have intersecting high-speed roadways, which can create

access management risks.

This section describes specific characteristics and

access management challenges and opportunities

associated with rural areas and intersections, and

provides a summary of potential access management

treatments that can improve the safety of motorists,

bicyclists, and pedestrians.

Physical characteristics of rural roads include divided

or undivided two-lane and multilane highways; paved

and unpaved shoulders; and infrequent full-access,

unsignalized, and on occasion, signalized intersections.

Traﬃc characteristics include speeds of 50 mph and

higher. Pedestrian and bicycle volumes are typically

the lowest on rural roads as compared to urban and

suburban roadways. Rural areas may be subject to

development in the future. TTI has published research

on rural intersections that relates driveway frequency

FHWA | Access Management in the Vicinity of Intersections 12

to crash frequency. Researchers estimate that a rural

signalized intersection with no driveways within 250 feet

“will be associated with 13 percent fewer crashes than an

intersection with three driveways (say, two driveways on

one major-approach and one on the other approach).”

Researchers also estimate that a rural unsignalized

intersection with no driveways within 250 feet will

be associated with 20 percent fewer crashes than an

intersection with three driveways [9].

2.3.2 Potential Access Management Treatments to Improve Safety for Motorists in Rural Areas

The following access management approaches can help

to improve motorist safety and mobility at access points

implemented in the vicinity of intersections in rural areas:

• Early participation by jurisdictional staﬀ and all stakeholders

in planning processes can help assure that access requests

do not become problematic for regulating jurisdictions.

As development occurs in rural areas, a potential concern

is development of subdivisions or partitions of large

properties near rural intersections that could create a

demand for additional access to the major roadway. Early

communication and coordination with property owners can

help to establish the location and number of driveways that

can be permitted to the major roadway as part of the land

subdivision process.

• Provide adequate throat depth and on-site circulation for

vehicles to easily exit a major roadway. This will minimize

speed diﬀerential between through vehicles and vehicles

slowing to turn into a driveway.

• Pave the shoulders near driveways to provide additional

entry and exit width and, hence, higher entry and exit

speeds to help minimize speed diﬀerentials between

through vehicles and vehicles turning onto or oﬀ of the

roadway within the functional area of an intersection.

• In situations where there are higher traﬃc generators in the

vicinity of rural intersections, frontage roads that parallel

the major roadway may also be employed as a means to

provide access to each of the adjacent properties. This

solution can help to eliminate several access points to the

major roadway as access to each development is achieved

via the frontage/backage road rather than to the major

roadway. In instances where the intersecting roadway

has high traﬃc volumes, the jurisdiction may elect to

implement some type of grade-separated facility rather

than allow the installation of a traﬃc signal on a high-speed

corridor.

2.3.3 Potential Treatments to Improve Safety for Pedestrians, and Bicyclists in Rural Areas

In rural areas, where there is no sidewalk, pedestrians

and bicyclists beneﬁt from roadway shoulders that are

at least 4 feet wide or wider, paved and well maintained.

As access and intersection modiﬁcations are considered

in these environments, to the extent possible, shoulder

widths should be maintained in order to provide facilities

for non-auto travelers. Figure 14 depicts an example of a

paved shoulder for bicycles or pedestrians on a rural road.

Photo: Kittelson & Associates, Inc. (used with permission)

Figure 14: Paved shoulder for bicycles or pedestrians

FHWA | Access Management in the Vicinity of Intersections 13

Section 3: References

The following documents were referenced in the development of this technical summary.

1. Roundabouts: An Informational Guide, Report FHWA-RD-00-067. FHWA, U.S. Department of Transportation, June

2000. This comprehensive guide is anticipated to be published in 2010. It will include the most recent research

and ﬁndings for the design and implementation of roundabouts in the U.S.

2. A Policy on Geometric Design of Highways and Streets, AASHTO 2004. Commonly referred to as the “Green Book,” this

manual provides the transportation professional with a wide array of guidelines for the design and operation of

roadways and streets.

3. Access Management Manual, Transportation Research Board. Washington, D.C. 2003. A comprehensive overview

on access management, the Access Management Manual provides information on how to develop a State or local

access management program. The manual also includes sections on corridor management, land development,

access location and spacing criteria, medians, public involvement, right-of-way and legal concerns, driveway

applications and permitting processes, and case studies.

4. G. Schultz, C. Allen, and D. Eggett. Crashes in the Vicinity of Major Crossroads, Brigham Young University,

Department of Civil and Environmental Engineering for the Utah Department of Transportation, December 2008.

The study focuses on the evaluation of crashes in the vicinity of signalized -intersections in suburban areas.

5. J. Bonneson, K. Zimmerman, and K. Fitzpatrick, Roadway Safety Design Synthesis, Texas Transportation Institute,

November 2005. This document describes the eﬀect of key design components on street and highway safety.

6. Analysis of Crossing Path Crashes, U.S. Department of Transportation. July 2001. This 76-page report examines

crossing path crashes within the physical area of an intersection, including contributing factors to the crashes

and a section on pedestrian and bicyclists’ crashes at intersections.

7. Report 420, Impacts of Access Management Techniques, Transportation Research Board. Washington, D.C. 1999. This

170-page report presents access management techniques and provides methods for estimating the safety and

operational eﬀects of diﬀerent techniques. The report was a precursor to the 2003 Access Management Manual.

8. Florida Driveway Information Guide, Florida Department of Transportation, September 2008 (http://www.dot.state.

ﬂ.us/planning/systems/sm/accman/pdfs/driveway2008.pdf). This guide provides a comprehensive overview

on issues related to driveways including information on appropriate connection radii and ﬂare, driveway width,

grade and length, sight distance considerations, optimum location for a driveway, and pedestrian considerations.

9. J. Bonneson, K. Zimmerman, and K. Fitzpatrick, Roadway Safety Design Synthesis, Texas Department of

Transportation, 2005. The synthesis includes safety information related to freeways, interchange ramps, rural

highways and intersections and urban streets and intersections.

FHWA | Access Management in the Vicinity of Intersections 14

The following web sites oﬀer two of the most comprehensive portals available for online access management

information:

• FHWA Access Management Web site: http://www.ops.fhwa.dot.gov/access_mgmt/resources.htm

The web site provides links to FHWA resources and publications published on access management topics, including

videos/CDs; brochures, including the Beneﬁts of Access Management (2003); the publication Safe Access is Good for

Business (2006), with accompanying CD; contact information for the National Highway Institute 3-day classroom

course “Access Management, Location and Design”; and a link to the Access Management Manual at the TRB Bookstore.

The FHWA materials and classroom course will be especially beneﬁcial for those involved in public outreach and

coordination and those desiring to learn more about the technical and legal aspects of an access management

program.

• TRB Access Management Committee: http://www.accessmanagement.info/

The site includes information on all of the access management related publications that have been developed within

the United States and many other countries in the past two decades. The site provides links to published research

(including NCHRP reports); guides and handbooks for the practitioner; outreach materials; papers, PowerPoint and

video presentations from past access management conferences; information on upcoming conferences and future

research needs; and policies and programs from international, state, and local agencies.

FHWA | Access Management in the Vicinity of Intersections 15

For More Information

Jeffrey Shaw

Intersection Program Manager,

FHWA Office of Safety

202.738.7793

jeffrey.shaw@dot.gov

Visit FHWA’s intersection safety web site to download this

and other technical outreach products highlighting proven

intersection safety treatments from across the country:

http://safety.fhwa.dot.gov/intersection

FHWA-SA-10-002

Updated July 2020