http://safety.fhwa.dot.gov

Intersection Proven Safety Countermeasure 

Technical Summary: 

Corridor Access Management 
 

 

Foreward 

In 2012, the Federal Highway Administration, Offce of Safety issued a “Guidance 

Memorandum on Promoting the Implementation of Proven Safety Countermeasures”. 

This guidance took into consideration the latest safety research to advance a group 

of countermeasures proven highly effective at improving safety.The nine Proven Safety 

Countermeasures chosen for targeted implementation included Corridor Access 

Management, defned as “a set of techniques that State and local governments use to 

control access to highways, major arterials, and other roadways.” This included all types of 

access, ranging from high volume, suburban signalized intersections to simple, unpaved 

rural driveways, along all classes of roads and highways open to public travel. 

As a means to further promote and advance Corridor Access Management, this 

Technical Summary and a companion Executive Summary have been prepared to assist 

transportation professionals with decisions pertaining to Corridor Access Management, 

including planning, permitting, design, selection, and implementation.This document 

provides a substantive overview of important access-related issues: safety performance 

(i.e. crashes), effects on pedestrian and bicycle facilities, and community and business 

economic impacts. More information on Corridor Access Management can be found on 

the FHWA website at http://safety.fhwa.dot.gov. 

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

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. 

ii 
Contents 

Managing access at the corridor level improves safety and business ........................ 1 

Addressing the concerns about Corridor Access Management 

improvements with data........................................................................................ 2 

Reducing confict points and improving safety ............................................................. 3 

Confict points ...................................................................................................................................3 

Access points....................................................................................................................................3 

Driveways...........................................................................................................................................3 

Reducing crashes ............................................................................................................ 4 

Offering a range of design options................................................................................. 6 

Relocation of Direct Left Turns ..........................................................................................................6 

Provision of Turn Lanes ......................................................................................................................7 

Median Type......................................................................................................................................7 

Signal density....................................................................................................................................8 

Unsignalized Access Density............................................................................................................9 

Benefting pedestrians and cyclists................................................................................. 9 

Improving operations for all stakeholders..................................................................... 11 

Roundabouts ..................................................................................................................................12 

Innovative Intersection Corridors ...................................................................................................12 

Overcoming potential challenges ................................................................................ 13 

Setting Enabling Policy ...................................................................................................................13 

Identifying Funding.........................................................................................................................14 

Managing Access During Construction........................................................................................14 

Building Stakeholder Support ........................................................................................................15 

Demonstrating Economic Benefts.................................................................................................15 

Helping stakeholders share your vision......................................................................... 15 

Highway 101 Case Study, Shakopee, Minnesota ......................................................... 18 

Endnotes......................................................................................................................... 20 

iii 

Managing access at the corridor level improves safety and business 

Imagine a multilane urban/suburban roadway where traffc is heavy, yet moves well; 

accommodates drivers, pedestrians, and bicyclists; allows easy entry to and exit from 

businesses and other destinations; and has fewer crashes and other conficts. Chances are 

this road is beneftting from Corridor Access Management (CAM), a strategy that seeks an 

appropriate balance between the safety and mobility of a roadway facility with the access 

needs of adjacent land uses. 

While managing access at a single location may help improve safety and operations 

within an immediate vicinity, CAM has been shown to improve safety, mobility, accessibility, 

and even business along an entire stretch of roadway because it favorably impacts ALL 

properties along that corridor. 

CAM preserves the fow of people and freight, and enables safe access to businesses 

and neighborhoods using a combination of policies and strategies, such as closing, 

consolidating, or improving driveways, median openings, and intersections; adding or 

redesigning medians; and planned spacing of intersections, median openings, and 

driveways. CAM may also employ the use of frontage roads to create a safer, more effcient 

system. 

Studies conducted by State and local agencies, national organizations, and transportation 

trade associations consistently show that access management notably improves traffc fow 

and safety for travelers. In addition, strong evidence shows that CAM can ultimately improve 

business in many cases. 

Exhibit 1: Washington State Department of Transportation (WSDOT) conducted an analysis of the crashes in the corridor before 

and after the measures were in place.The results of the analysis showed that implementing access management practices 

signifcantly reduced accident severity and societal costs. (Source: WSDOT) 

1 
 

 

 

Addressing the concerns about Corridor Access Management 

improvements with data 

Business owners along a corridor may fear that access management improvements will 

disrupt or otherwise negatively impact their businesses, but several studies over many 

years have dispelled this myth.When surveyed after an access management project, most 

property owners do not report any long-term adverse effects on their property value or 

business. In fact, making the locations easier and safer to access can actually have positive 

effects. For example: 

• A	study	of	property	values	on	Texas	corridors	with	access	management	projects	found

that land values stayed the same or increased, with very few exceptions.1 

• More	than	70	percent	of	the	businesses	impacted	by	a	project	in	Florida	involving

several median opening closures reported no change in property value, while 13 

percent reported some increase in value.2 

• A	2005	study	of	commercial	property	values

along a major access management project in 

Minnesota found that property values depend 

more on the strength of the local economy 

and the general location of the property in the 

metropolitan area; changes in access seemed 

to have little or no effect on the value of parcels.3 

“...poorly designed entrances 

and exits at shopping centers not 

only present a safety concern, 

but also cause congestion that 

can create a negative image of 

the center.” 

• A	study	of	Kansas	properties	impacted	by	

access changes found that the majority were 

suitable for the same types of commercial uses 

after the access management project was 

completed.This was true even for businesses that had direct access before the project 

and access only via frontage roads after project completion.4 

—FHWA, 

Safe Access is Good for Business7 

• A	1996	study	of	business	vitality	in	five	Iowa	communities	found	that	after	CAM

improvements total retail sales increased in all fve communities, ranging from 5.5 

percent to 346.2 percent.5 

Recently, the North Carolina Department of Transportation (NCDOT) conducted a study 

in conjunction with its efforts to reduce collisions and increase capacity along strategic 

highway corridors across the State.6 The NCDOT study examined different corridor access 

management techniques, including replacing two-way left-turn lanes with raised medians, 

closing median openings, and installing super streets. Prior to construction, comments from 

businesses along these corridors indicated a concern that the new designs would limit direct 

access to their properties and result in a negative economic impact. Many business owners 

contended that median-divided roadways limit the ability of potential patrons to access their 

businesses. 

However, the study concluded that these same business owners later viewed the access 

management improvements in a more positive light than businesses on roadways where 

CAM techniques had not been implemented.The study compared revenues for businesses 

along corridors that had CAM treatments and those that did not.There was no evidence 

that CAM installations created negative economic impacts. 

2 
Reducing confict points and improving safety 

Confict points. Corridor access management has been shown to improve safety by 

reducing, managing, and separating confict points, which increases available response 

time for all roadway users, including pedestrians and bicyclists. Safety benefts have 

also been attributed to certain improvements in traffc fow. In particular, improved traffc 

operations can engender more consistent driver behavior and reduce aggressive actions, 

such as speeding, red light running, and failing to yield the right-of-way. 

Exhibit 2: At this location, corridor access management measures were implemented to reduce crashes at median crossovers. 

Flexible post-mounted delineators were installed to restrict direct left turns from the side street.The photo on the left shows the 

main street and two vehicles in the median turning left onto the side street.The photo on the right shows how the delineators 

were placed to prevent vehicles from turning left through the median onto the main street. (Source:VHB) 

Access points. The FHWA found that poorly designed entrances and exits at shopping 

centers not only present a safety concern, but also cause congestion that can create a 

negative image of the center.8 A national study in the late 1990s looked at nearly 40,000 

crashes and data from previous studies to determine the crash rate associated with adding 

access points to major roads. It found that an increase from 10 to 20 access points per 

mile on major arterial roads increases the crash rate by about 30 percent.The crash rate 

continues to rise as more access is permitted.This is why studies consistently show that wellmanaged arterials are often 40 to 50 percent safer than poorly managed routes. 

Driveways. The Highway Safety Manual (HSM) also provides some measures for determining 

the effect of driveways on safety.The HSM contains models for estimating expected average 

crash frequency for specifc roadway features.These models, called safety performance 

functions (SPF), are equations that estimate predicted average crash frequency as a 

function of traffc volume and other roadway characteristics.The HSM has models to 

estimate predicted average crash frequency for the following types of facilities: 

• Rural	two-lane,	two-way	roads	(Chapter	10	in	the	HSM)

• Rural	multilane	highways	(Chapter	11	in	the	HSM)

• Urban	and	suburban	arterials	(Chapter	12	in	the	HSM)

The HSM only has methods that model the safety effects of driveways for rural two-lane, 

two-way roads and urban and suburban arterials. For rural two-lane, two-way roads the 

base condition for driveway density is fve driveways per mile. If driveway density is less than 

fve driveways per mile, then the base condition applies and the predicted average crash 

frequency is not adjusted for driveway density. However, for driveway densities greater than 

3 
fve driveways per mile, the predicted average crash frequency will increase in accordance 

with the SPF in the HSM (Equation10-17). 

Exhibit 3: Graphical form of the SPF for Multiple Vehicle Driveway Related Collisions on Two-Lane Undivided Arterials. (Source: 

AASHTO Highway Safety Manual) 

On urban and suburban arterials the frequency of driveway-related collisions on a roadway 

segment depends on the number and type of driveways. In general, higher driveway 

densities result in higher crash frequencies.The HSM reports that reducing the driveway 

density can reduce crashes by up to 31 percent (Table 13-58 in the HSM).The effect of 

driveway type on crash frequency is illustrated in Exhibit 3 where seven specifc driveway 

types have been modeled for two-lane, undivided arterials. 

Reducing crashes 

For more information 

A	Kentucky	Transportation	Cabinet	study	showed	that	 on HSIP eligibility 

a strategic, comprehensive access management 

program can reduce total Statewide annual crashes 

by an estimated 20 to 50 percent.9 Another study 

in Michigan reported a 61 percent reduction in the 

number of crashes when left turns were prohibited 

along a corridor and replaced with U-turn designs like 

those described in Exhibit 9.10 

Direct specifc HSIP eligibility 

questions to the FHWA Division 

offce in your State.A list 

of FHWA Division offces is 

available at www.fhwa.dot. 

gov/feld.html. 

And more information is 

available at http://safety. 

fhwa.dot.gov. 

4 
 

 

Medians and Super Streets 

Medians. Medians are the areas located 

between opposing lanes of traffc. Medians 

separate various road users and can be 

open, meaning that they are defned 

with pavement markings, or channelized, 

meaning that it is physically raised through 

the use of curb.11 

Median openings. Breaks in the median to 

allow for turning movements or intersections. 

Super Streets. Also known as Restricted 

Crossing U-turns (RCUT), J-turns, and 

Reduced Confict Intersections. Similar to 

left-over, or directional-median crossovers, 

this type of intersection prohibits left-turn 

and through movements from side street 

approaches.12 Instead, drivers on the minor 

approach must turn right onto the main 

road and then make a U-turn maneuver 

at a one-way median opening after the 

intersection. Left turns from the main 

road approaches may be executed in a 

manner similar to left turns at conventional 

intersections or they could be removed, 

requiring drivers to utilize the median 

opening for a U-turn maneuver.This type 

of intersection is well-suited for use along 

arterials at intersections with comparatively 

lower volume roads. 

Exhibit 5: Flush median. (Source: VHB) 

Median opening to allow 

for turning movements 

Median opening to allow 

for intersection 

Exhibit 6: Example of median breaks along U-turn 

corridor on Woodward Avenue in Detroit, Michigan. 

(Source: Google Earth) 

Exhibit 4: Raised median. (Source: VHB) 

Exhibit 7: Basic super street intersection. (Source: FHWA) Exhibit 8: Super street intersection with left-turn 

movements. (Source: FHWA) 

5 
Offering a range of design options 

CAM design options allow agencies to deploy fexible solutions for their unique 

environments. Common CAM techniques and their safety benefts include: 

Relocation of Direct Left Turns. The restriction of direct left turns reduces conficts and 

improves safety along corridors.Where direct left turns are restricted by raised medians or 

other channelizing devices, left turns would be performed indirectly as follows: 

• Instead	of	direct	left	turns	into	access	points	along	the	mainline,	motorists	perform	a

U-turn at a designated location and then turn right. 

• Instead	of	direct	left	turns	out	of	access	points	along	the	mainline,	motorists	turn	right

and then perform a U-turn at a designated location. 

Exhibit 9: Example of 

method to relocate direct 

left turns.13 (Source: FHWA) 

Restricting left-hand turns reduces conficts and improves safety along corridors. 

• Making	a	U-turn	at	a	median	opening	to	get	to	the	opposite	side	of	a	busy	highway

is approximately 25 percent safer than a direct left turn from a side street or other 

access point.14 

• In	a	Florida	study,	the	number	of	conflicts	per	hour	was	reduced	by	nearly	50	percent

after replacing a direct left turn with a right turn followed by U-turn (RTUT) (Lu and 

Williams 2001, Page ii).15 

• For	indirect	turn	intersections,	crashes	were	reduced	by	20	percent	on	average	and	35

percent if the indirect turn intersection was signalized (Gluck et al., 1999). 

• The	Highway	Safety	Manual16 summarizes the crash reduction effects as follows: 

Total: 14 to 51 percent reduction 

PDO: 5 to 11 percent reduction 

Fatal/Injury: 31 to 36 percent reduction 

Rear-end: 9 to 16 percent reduction 

Right Angle: 33 to 36 percent reduction 

Sideswipe: None reported 

6 
Provision of Turn Lanes. When restricting direct left turns, it is necessary to provide 

adequate U-turn opportunities through median openings or designated left-turn lanes at 

intersections. Providing exclusive turn lanes is critical to the safety and operations of U-turn 

opportunities, but also helps to improve safety and operations for typical left- and right-turn 

maneuvers. 

Exhibit 10: Example of 

exclusive turn lanes used 

to separate slower turning 

vehicles from through traffc. 

(Source: VHB) 

Turn lanes help to separate the turning traffc from the through traffc along the 

mainline. 

• Adding	an	exclusive	left-turn	lane	results	in	a	reduction	in	total	crashes	(7	to	44

percent) and fatal and injury crashes (6 to 55 percent) at rural and urban stop- and 

signal-controlled intersections. 

• Adding	an	exclusive	right-turn	lane	results	in	a	reduction	in	total	crashes	(4	to	14

percent) and fatal and injury crashes (9 to 23 percent) at rural and urban stop- and 

signal-controlled intersections.17 

Median Type. The type of median determines the type of turning movements that can 

be performed along a corridor and separates turning movements and opposing traffc. 

Median improvements include: 

• A	two-way	left-turn	lane	(TWLTL)	to	provide	lateral	separation	between	opposing	traffic,

yet allow the full complement of turning movements (e.g., left turns into and out of 

access points). However, it offers no refuge for crossing pedestrians, and loses safety 

effectiveness as the number of through lanes increases along the roadway (e.g., from 

one through lane in each direction to two through lanes in each direction). 

• A	raised,	non-traversable	median	to	provide	physical	separation	between	opposing

directions of traffc, but restrict left turns into and out of access points unless median 

openings are provided.A raised median implemented to manage access can also 

provide pedestrian refuge islands, both at intersections and at mid-block locations. 

These medians allow for a two-stage crossing, in which pedestrians cross one direction 

of traffc at a time, thus shortening crossing distances and reducing the complexity of 

the crossing task.This is especially true at transit stops, where pedestrians are regularly 

expected, but uncontrolled multilane crossings are common. 

7 
Exhibit 11: (top) undivided roadway; (middle) two-way left-turn lane; 

(bottom) raised median. (Source:VHB) 

An undivided highway provides no separation 

between opposing traffc, does not restrict 

turning movements into and out of access 

points, and offers no refuge for pedestrians. 

• Converting	a	TWLTL	to	a	non-traversable	median

reduces total crashes by 15 to 57 percent18 and 

reduces injury crashes by 33 to 48 percent.19 

• Installing	a	TWLTL	on	an	undivided	roadway

reduces crashes by 13 to 70 percent (Hallmark 

et al. 2008).20 

• Installing	a	non-traversable	median	on	an

undivided roadway reduces crashes by 21 to 

53 percent.21 

• Raised	medians	are	associated	with	a	45

percent reduction in pedestrian crashes and 

78 percent reduction in pedestrian fatalities.22 

• A	study	of	corridor	access	management

by Gross et al. (in press) reports that the 

installation of a non-traversable median 

reduces right-angle crashes along a corridor 

by 38 percent. 

Signal Density. Signal density is defned as the number of signalized intersections per mile 

along a given corridor. More signals create more access points, which add confict points 

and increase the potential for crashes and incidents involving pedestrians and bicyclists. 

For pedestrians, every signalized intersection represents at least four potential confict 

points depending on the number of approaches and allowable movements.While crashes 

tend to increase with signal density, there is the potential to mitigate these crashes by 

interconnecting and coordinating the signals. 

Increased signal density contributes 

to substantially higher crash rates. 

A study of corridor access 

management by Gross et al. (in 

press) reports that total corridor 

crashes increase by 10 to 13 percent 

for each additional signal per mile 

depending on the adjacent land 

use (e.g., commercial, residential, or 

mixed use). 

Exhibit 12: Example of closely spaced signals. (Source:VHB) 

8 
Exhibit 13: Diagram illustrating confict points associated with unsignalized accesses.23 

(Source: FHWA) 

Unsignalized Access Density. Unsignalized access density is 

defned as the number of unsignalized access points per mile 

along a given corridor, and include driveways, unsignalized 

crossroads, and median openings. Crash rates and crash 

severity increase as the unsignalized access density increases. 

Again, because access points add confict points, the potential 

for crashes and incidents involving pedestrians and bicyclists 

increases.The fewer access points per mile, the fewer potential 

conficts for all roadway users. 

Crash rates and 

crash severity 

increase as the 

unsignalized access

density increases. 

• Each	additional

access point per

mile increases the 

crash rate by about 

3 percent (Green 

Book, Section 2.5.5). 

• A	study	of

corridor access 

management 

by Gross et al. 

(in press) reports 

that total corridor 

crashes increase 

by approximately 

5 percent for 

each additional 

unsignalized access 

point per mile. 

Benefting pedestrians and cyclists 

Research indicates that several key access management 

techniques are just as valuable to pedestrians and bicyclists 

as they are to motorists. Each driveway represents four potential 

confict points for pedestrians and bicyclists when all turning movements are permitted in 

and out of the location.This is critical because the presence of driveways is the primary 

reason for crashes involving pedestrians walking on the sidewalk.Techniques to reduce 

the number of confict points or reduce exposure (i.e., crossing distance) for pedestrians 

walking on the sidewalk or bicyclists traveling in the roadway include: 

• Reducing	the	number	of	driveways,	particularly	commercial	driveways,	within	a	given

distance (per block or mile). 

• Reducing	the	number	of	conflict	points	at	driveways	(e.g.,	converting	driveways	to	rightin, right-out or installing a median that restricts left turns in and out of driveways.) 

• Providing	for	greater	distance	between	driveways. Effects on Bicyclist Safety • Providing	a	safe	refuge	for	pedestrian	crossings

with raised medians. Studies show that a motorist 

failing to yield mid-block at a 

driveway or alley to a bicyclist 

accounted for between 8.6 

percent and 11.7 percent of 

all crashes involving a bicyclist 

and a motor vehicle.24 

Tools that assess conditions for pedestrians and 

bicyclists consider elements that are based on 

perceived safety.The TRB Highway Capacity Manual 

(HCM)25 addresses measures that combine safety 

and operations for pedestrians and bicyclists.The 

various level-of-service (LOS) models emphasize the 

9 
use of traveler perceptions of real-world 

conditions.These models have shown 

that corridor access and the presence of 

driveways play a critical role in perceived 

safety. For example, in the Urban Street 

LOS analysis methodology, the number of 

access points is considered a key input to 

the Bicycle Mode LOS model because of 

the potential for confict between cyclists 

traveling on the street and vehicles 

entering or exiting streets and driveways. 

The Bicycle Segment LOS degrades 

steadily along a linear progression as 

the number of access points increases. 

Interestingly, the number of access points 

has a signifcant effect on the Segment 

LOS, which can exceed the infuence 

of both the Bicycle Link LOS Score and 

Bicycle Intersection LOS Score. 

Exhibit 14: A corridor with closely spaced driveways creates 

a challenging environment for pedestrians and bicyclists. 

Pedestrians with mobility restrictions may be particularly affected 

by driveways through sidewalks.These locations require careful 

design and construction to ensure they meet requirements under 

the American with Disabilities Act (ADA). (Source:VHB) 

Exhibit 15: There are four potential conficting maneuvers between motorists and pedestrians, as well as motorists and bicyclists, 

for each access point along a roadway with no median.The majority of crashes involving pedestrians or bicyclists are a result 

of these conficts. (Source: FHWA) 

10 
Improving operations for all stakeholders 

CAM treatments improve traffc operations by helping 

increase throughput, reduce trip times and delay, keep 

travel speeds consistent—which may also contribute to 

reduced fuel consumption and vehicle emissions—and 

deliver better quality of service for all road users. As a 

beneft to businesses, customers may travel farther to 

a destination if the trip time is reasonable and reliable, 

thus potentially increasing market share. 

For instance, the TRB study Evaluating Alternative 

Operations Strategies to Improve Travel Time Reliability26 

shows that access management could reduce delay 

on	Kentucky’s	surface	street	system	by	46	million	hours	

per year with the largest delay saving on the Urban 

Class I and II roadways. 

• Urban Class I roads have high volumes and speeds, 

place a high priority on mobility and long distance 

travel through urban areas, and typically include 

principle arterials and multilane facilities that often 

have a median. 

• Urban Class II roadways have moderate volumes 

and speeds, place a priority on mobility, are used 

for intra-city travel, and typically include minor 

arterials that are often multilane facilities.27 

Incorporating Access 

Management as Emphasis 

Areas in SHSPs 

Many States have included 

access management as an 

emphasis area strategy in 

their Strategic Highway Safety 

Plan to address intersectionrelated crashes.These States 

include: 

• Nebraska

• Virginia

• Nevada

• Florida

• North	Dakota

• Minnesota

• New	York

• Pennsylvania

• Illinois

• Oklahoma

And the Texas Department of Transportation (TxDOT) Access Management Manual reports:28 

• Inadequate	access	management	can	increase	travel	time	and	delay	by	as	much	as	40

to 60 percent. A 10 percent reduction in average travel speeds can cause a business to 

lose 20 percent of its market 

area. 

• A	four-lane	divided	major

roadway with long, uniform 

signal spacing, directional 

openings between signals, 

and auxiliary lanes could 

accommodate a similar 

volume and similar quality of 

service as a six-lane divided 

roadway having traffc 

signals at 1⁄4-mile intervals, 

unregulated access between 

the signals, and no auxiliary 

lanes. 

Safety Fast Facts 

• Access	management	could	reduce	total

statewide annual crashes by more than 

20 percent.29 

• Access	management	could	reduce	total	crashes

by approximately 39 percent and rear-end and 

left-turn crashes by 41 percent and 42 percent, 

respectively.30 

• Proper	access	control	can	reduce	crashes	by

as much as 50 percent while capacity can be 

increased by 23 to 45 percent.31 

11 
Roundabouts. When deployed in a series, roundabouts can also improve operations and 

safety of a corridor. In Golden, Colorado, a series of four roundabouts and raised medians 

replaced four travel lanes and a two-way left-turn lane along Golden Road, a typical suburban 

arterial serving a strip commercial area.A report on the series of roundabouts found:32 

• Replacing	two	traffic	signals	with	four	roundabouts	resulted

in slower average speeds but an improvement in travel 

times of 13 percent (from 78 seconds to 68 seconds). 

• Delay	experienced	entering	or	exiting	business	accesses

was cut by at least 50 percent, with a reduction in average 

delay from 28 seconds to 13 seconds and a reduction in 

Access management 

programs in 90 cities 

in the US reduce 

delay by a total of 61 

million hours.33 

maximum delay from 118 seconds to 40 seconds. 

• Total	crash	rates	for	the	corridor	decreased	by	88	percent	after	installation	of	the

roundabouts, while injury crash rates decreased by 93 percent. 

• Growth	in	sales	tax	revenues	increased	60	percent.

• More	than	75,000	square	feet	of	retail/office	space	have	been	built	since	the

roundabouts were constructed. 

A study of two roundabout corridors described in NCHRP Report 772 Evaluating the 

Performance of Corridors with Roundabouts also found that crash frequency decreased on 

the corridors following the construction of roundabouts.34 These fndings are consistent with 

those reported elsewhere suggesting that this trend is likely to continue in a corridor context. 

Exhibit 16: A series of roundabouts in Golden, Colorado. (Source: LSC Transportation Consultants, Inc.) 

Innovative Intersection Corridors. Combining innovative intersection designs with raised 

medians in between can provide an effective means of improving traffc operations and 

enhancing safety within a corridor. One roundabout scenario—referred to as the “Dog-Bone” 

concept because of its geometric characteristics—converts all side streets and driveway 

access points within the segment to right-in/right-out confgurations by prohibiting left turns. 

The roundabouts at the end of the raised median segment allow safe U-turn maneuvers for 

motorists traveling to and from the side streets. 

12 
Exhibit 17: Example of the Dog-Bone concept. A single access point lies on 

the segment between the two roundabouts. A raised median separates the 

opposing through lanes on the mainline, which serves to prohibit all left 

turns between the roundabouts. The dotted arrow illustrates the path for a 

vehicle seeking to turn left from the driveway, while the orange arrow shows 

the path of a vehicle wishing to turn left into the driveway. (Source: VHB)

The Dog-Bone Concept 

The Dog-Bone concept 

would apply regardless 

of the number of access 

points and side streets 

located within the 

segment, with all U-turn 

maneuvers being safely 

accommodated by the 

roundabouts. 

The same can be accomplished using median u-turns (MUT) and restricted crossing u-turns 

(RCUT).The MUT has been used for decades throughout the State of Michigan, and in 

particular along high-volume routes in the Detroit metropolitan region.The RCUT has been 

used successfully in North Carolina to achieve a balance between safety, operations, and 

access along the corridors. 

Overcoming potential 

challenges 

Planning and implementing CAM 

improvements calls for careful 

policy making and pre-determined 

strategies for overcoming the 

inevitable challenges that arise with 

projects of this complexity, expense, 

and often controversy. 

Setting Enabling Policy. A common 

challenge arises when State and 

municipal agencies have not 

yet established effective policies. 

Often, the mechanisms do not 

exist to deny permits for accesses 

that could potentially increase confict points, and thus affect safety and mobility along 

a roadway. Agencies are encouraged to establish an access management policy that 

supports general corridor access management. 

In North Carolina, the Wilmington Metropolitan Planning Organization employed two 

notable practices: 

• A	Public	Involvement	Policy	that	specified	the	process	for	public	participation	in

transportation decision making.35 

Exhibit 18: Median U-turn (MUT) in Michigan. (Source: FHWA) 

13 
• A	Memorandum	of	Understanding	for	Cooperative,	Comprehensive,	and	Continuing

Transportation Planning that links NCDOT programs with the comprehensive plans of 

several municipalities.36 

The Iowa Department of Transportation utilized an Access Management Task Force 

composed of individuals from a variety of public and private organizations, including city, 

chamber of commerce, and DOT representatives.37 After assessing the benefts and impacts 

of access management projects in Iowa, the task force developed an Access Management 

Handbook that highlights the importance of incorporating access management into 

comprehensive planning. For those communities without a comprehensive plan, the 

handbook provides guidelines for developing a successful access management program. 

Identifying Funding. Paying for CAM improvements is a challenge, but there are options. 

Federal Highway Safety Improvement Program (HSIP) funds can be used for access 

management activities that address safety problems, such as changing median type, 

installing turn lanes, closing or relocating driveways and acquiring land.To qualify for HSIP 

funding,	CAM	improvements	must	(1)	address	a	priority	in	a	State’s	Strategic	Highway	

Safety Plan (SHSP), (2) be identifed through a data-driven process, and (3) contribute to a 

reduction of fatalities and serious injuries resulting from motor vehicle crashes. 

Fayetteville, North Carolina, successfully applied for HSIP funding to implement median 

improvements in several corridors where many serious crashes had occurred.The HSIP 

projects met the funding criteria and were selected based on beneft-cost analysis. 

Highway agencies in some localities have successfully partnered with other non-highway 

agencies and private developers to implement site-specifc and corridor access improvements. 

For	instance,	CAM	improvements	in	the	town	of	LeRay,	New	York,	resulted	from	a	collaborative

effort	funded	through	various	sources,	including	New	York	State	Department	of	Transportation

(NYSDOT),	the	Town	of	LeRay,	developers,	and	a	major	business	along	the	route.38 

Managing Access During Construction. Reduced access due to poor construction 

phasing can lead to negative perceptions of access improvements in general and in 

safety issues. Maintaining good access during construction reassures both road users and 

businesses that the improvements will result in better safety and mobility. A strong emphasis 

on maintaining good access will also help create and sustain a positive relationship with 

the stakeholders affected most during the construction period. 

Some localities utilize parallel, rear-access roads as a corridor access management strategy 

during construction. Designed to have little or no impact to the existing access points, 

rear-access roads can be existing roads that are improved or roads that are specifcally 

constructed. If the rear-access road is improved or constructed before closing access along 

the front of the properties, then construction will have little impact on access. In some 

situations, access may be maintained along perpendicular side streets during construction. 

Frequent communications with business owners during construction is key to helping 

identify problem areas and maintaining focus on a shared vision for improvements. Owners 

14 
 

should be kept apprised of the overall construction schedule and ongoing construction 

activities. Routine meetings where owners can provide feedback may also help maintain 

a collaborative environment. Often, establishing agreements in writing with local business 

owners helps alleviate concerns. 

Building Stakeholder Support. Change can lead to uncertainty, which in turn can result in 

hesitation and even outright resistance. Business owners may fear that construction and 

the improvements themselves will discourage customers from patronizing the businesses, 

negatively impacting 

revenue and economic 

viability. Residents of nearby 

neighborhoods may fear 

that their property values 

will go down or that safety 

will be compromised. 

Political leaders may resist 

supporting CAM strategies, 

fearing backlash from 

local businesses and voter 

constituencies. 

State and local transportation 

agencies can successfully 

anticipate and meet these 

fears and garner support 

by frst listening carefully to, 

and then staying in close 

communication with, the 

many stakeholders affected 

by CAM improvements. 

Stakeholder Involvement Plan in Minnesota 

A Minnesota DOT project of extensive improvements for 

a stretch of Highway 101 in Shakopee near Minneapolis 

called for an array of communications tactics to build 

stakeholder support.The project planners developed a 

Stakeholder Involvement Plan that included a number 

of mechanisms designed to build support among 

members of the public and businesses along the 

corridor.These mechanisms included: 

• Creating	a	Corridor	Advisory	Committee

• Holding	public	informational	meetings

• Conducting	City	Council	workshops,construction

staging workshops, and visual quality workshops 

• Meeting	with	individual	property	owners

• Appointing	a	business	liaison

Demonstrating Economic Benefts. To address misconceptions about economic impacts, 

agencies must be prepared to present data that link access management to economic 

improvements	for	the	corridor.	Studies	conducted	in	Texas, Florida,	Minnesota,	Kansas,	Iowa,

and North Carolina described on page 2 of this technical summary are valuable resources. 

It may also be helpful to study the specifc, local impact of the project that is the focus of 

the outreach. 

Helping stakeholders share your vision 

Visualization tools can enhance communication with multiple stakeholders by rendering 

a design, data, or other information in an easily understood visual format. One such tool 

is the Corridor Visualization Explorer (CVE),39 which can facilitate planning and outreach 

and support the decision-making process by illustrating the effects of various access 

management strategies. Using sliding indicators to select corridor characteristics (such as 

15 
 

 

 

 

number of lanes and signals per mile) and traffc conditions (number of vehicles per time 

period), the tool estimates the number of confict points, delay time per vehicle, potential 

crashes, and economic impact of the modeled changes, based on various research 

fndings. 

The virtual, graphics-based nature of the CVE helps agencies communicate access 

management concepts to the public.The tools provide visual display of the effects 

of access management decisions on a corridor, facilitating a more engaging and 

collaborative relationship between the public and those organizations trying to employ 

CAM techniques.This helps set the stage for a more productive process. 

Successful Stakeholder Involvement in Michigan 

Michigan has had successful and positive experiences working with local businesses 

and stakeholders when implementing access management strategies. One example of 

their ability to garner support was on a particular rehabilitation project that had a high 

rate of access-related crashes.The Michigan Department of Transportation (MDOT) staff 

met one-on-one with individual property owners to review the crash data and physically 

demonstrate, using a can of spray paint, how access points could be re-designed and 

made safer. MDOT then monitored and compared the before-and-after crash data and 

were able to show a signifcant reduction in access-related crashes along the project 

corridor. 

Another project was initiated by the planning commission of a township adjacent to a 

large urbanized area.The planning commission contacted MDOT to request assistance 

in creating a corridor access management plan and ordinance along a State highway 

that bisected the township.Township staff and planning commission members met 

frequently with local businesses, property owners and citizens to educate them about 

how the plan and ordinance would beneft their community. Crash information and 

access management concepts were shared with local businesses to explain how they 

could better protect their customers—allowing them to enter and leave the businesses 

more safely.The plan and ordinance were designed to implement changes in access 

over a period of time when changes in land use occur or when future road and utility 

projects create opportunities to implement the new design standards. 

The	key	to	Michigan’s	success	in	achieving	stakeholder	support	for	access	

management is to meet individually with property owners to explain the process, why 

changes are necessary, and to illustrate, physically or otherwise, the strategies that will 

be implemented. 

—Tom Doyle, Program Manager, Michigan Department of Transportation 

16 
The corridor visualization explorer is a tool that can help agencies communicate access management

concepts to the public. The tool provides a visual display of the effect of access management decisions

on a corridor. This tool is of great interest to FHWA and can be found here:

http://teachamerica.com/cve/cve.html

This is the fist page where the user selects the basic roadway conditions:

17

LADOTD and the CVE Tool 

The Louisiana Department of Traffic and Development (LADOTD) sponsored a 

project to create a visualization prototype that can be used to improve how access 

management principles are conveyed to the public.40

Exhibit 19: On the CVE Scenario Selection Screen, the user selects the basic roadway conditions. (Source: Teach 

America)

Exhibit 20: On the CVE Road Characteristics, Traffic Conditions and Consequences Screen, the user selects road 

and traffic conditions in the top pane. These are visualized in the middle pane. The effects of these decisions can 

be seen on the dials in the bottom pane, which also includes a note to the user. Dragging the cursor over the dials 

reveals explanations of the results. (Source: Teach America)

Select your scenario:

• Two Lane Urban

• Four Lane Undivided

• Four Lane with Two-way

• Left Turn Lane

• Six Lane Divided

Road Characteristics:

(number of lanes, 

driveways, roundabouts, 

signals, etc.)

Traffic Conditions: 

(vehicles per day, and 

transit buses per hour)

Consequences: 

(conflict points, seconds 

of delay per vehicle, 

quality of service, crashes, 

economic impact)

Selected Scenario

Four Lane Undivided

(serves roughly 25,000 

vehicles each day. 50 

driveways per mile)
Highway 101 Case Study, Shakopee, Minnesota 

CHARACTERISTICS: Highway 101 was originally a four-lane, undivided highway with 

shoulders, curbs, and gutters, unlimited accesses, and some historic and residential 

buildings. Highway 101 is a multi-functional transportation corridor that serves the 

region, as well as local business, residential, and recreational users. 

FUNDING: The project was mainly funded with State Trunk Highway Turnback funds, 

along with some shared costs between the city and county. 

APPROACH: For the frst six to eight months after the project was initiated, offcials 

met monthly to discuss issues and reach consensus on problems before discussing 

potential alternatives or solutions. 

INITIAL OPTIONS: Offcials considered using one-way pairs, four-lane divided 

corridor in a wider right-of-way, and reconstruction of existing corridor with access 

management. 

ALTERNATIVES: Within the existing 80-foot right-of-way, the county supported a 

four-lane with median design, while city offcials and businesses supported a fve-lane 

undivided design.The county agreed to the fve-lane undivided design, if city offcials 

and businesses would support “aggressive access management.” 

Exhibit 21: Car wash before CAM. Exhibit 22: Car wash after CAM. 

STAKEHOLDER INVOLVEMENT: In addition to the successful engagement of the 

business community early on, offcials met with individual property owners about 

specifc access conditions. Parcel-by-parcel, offcials negotiated with property owners 

on access management. Questions raised included: 

• How	are	existing	accesses	being	used?

• How	are	customers	entering	and	exiting	the	site?

18 
• How	are	deliveries	accessing	the	site?

• What	else	needs	to	change	if	site	access	changes?

Concept drawings and renderings of access management strategies were 

developed with business owner input. 

POLICY/PREREQUISITES: According to Minnesota statute, property owners are entitled 

to compensation if 51 percent or more accesses are removed.Traditional right-of-way 

acquisition compensated for almost all access revisions. 

The county offered to include site circulation mitigation in the project for properties 

where access was closed or revised.The offer was contingent upon the property 

owner granting a right-of-entry agreement or temporary easement at no cost to the 

county. 

RESULT: Based on a decision-making process developed by staff, 26 of the 41 private 

property accesses were identifed for potential closure.Through further investigation 

and negotiation with individual property owners, 20 of the 26 private property 

accesses were removed. Exhibits 21 through 24 show before and after images of 

some of the properties. Many of these property owners have recognized improved 

site access and circulation as a result of this approach.The Chamber of Commerce 

praised staff for its willingness to work with business owners and accommodate their 

interests in the planning, design, and construction of the project. 

Exhibit 23: Fast food restaurant before 

CAM. 

Exhibit 24: Fast food restaurant after CAM. 

19 
Endnotes

1 Eisele, W. L. and W. E. Frawley, A Methodology for Determining Economic Impacts of Raised Medians: Data Analysis on Additional Case Studies, Report 3904-3. Texas Transportation Institute, October 1999. (https://rosap.ntl.bts.gov/view/dot/4794) 

2	 FHWA,	Benefits	of	Access	Management	Brochure,	FHWA-OP-03-066,	April	2013.	(https://ops.fhwa.dot.gov/access_mgmt/ 

docs/benefits_am_trifold.pdf) 

3	 FHWA,	Safe	Access	is	Good	for	Business,	FHWA-HOP-06-107,	August	2006.	(http://www.teachamerica.com/amv/Primer%20

for%20Print.pdf) 

4 Ibid. 

5	 Center	for	Transportation	Research	and	Education	(CTRE),	Access	Management	Awareness	Program	Phase	II	Report,	December 1997. (http://publications.iowa.gov/17191/) 

6	 Cunningham,	Christopher	M.,	et	al,	Economic	Effects	of	Access	Management	Techniques	in	North	Carolina,	Project:	2009-

12, December 2010. (http://digital.ncdcr.gov/cdm/ref/collection/p249901coll22/id/221356) 

7 FHWA, Safe Access is Good for Business. (http://ops.fhwa.dot.gov/publications/amprimer/access_mgmt_primer.htm) 

8 Ibid. 

9	 Stamatiadis,	N.,	et	al,	Access	Management	for	Kentucky,	Research	Report	KTC-04-05/SPR251-01-1F,	Kentucky	Transportation

Center,	Lexington,	KY.	February	2004.	(https://uknowledge.uky.edu/cgi/viewcontent.cgi?article=1217&context=ktc_researchreports) 

10	 Hallmark,	S.,	et	al.	Toolbox	to	Assess	Tradeoffs	between	Safety,	Operations,	and	Air	Quality	for	Intersection	and	Access	Management	Strategies,	MTC	Project	2007-02,	Center	for	Transportation	Research	and	Education	(CTRE),	Iowa	State	University,

Ames,	IA,	November	2008.	(https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1150&context=intrans_reports) 

11 FHWA,	Safety	Benefits	of	Raised	Medians	and	Pedestrian	Refuge	Areas,	FHWA-SA-10-020.	(https://safety.fhwa.dot.gov/ 

ped_bike/tools_solve/medians_trifold/) 

12	 FHWA,	“Chapter	4.	Restricted	Crossing	U-Turn	Intersection,”	Alternative	Intersections/Interchanges:	Informational	Report

(AIIR),	FHWA-HRT-09-060,	April	2010.	(http://www.fhwa.dot.gov/publications/research/safety/09060/004.cfm) 

13	 FHWA,	“Chapter	8.	System-Wide	Treatments,”	Signalized	Intersections:	An	Informational	Guide,	FHWA-SA-13-027,	Washington, DC. July 2013. (https://safety.fhwa.dot.gov/intersection/conventional/signalized/fhwasa13027/ch8.pdf) 

14 FHWA, Safe Access is Good for Business. (http://ops.fhwa.dot.gov/publications/amprimer/access_mgmt_primer.htm) 

15	 Lu,	J.,	et	al.,	Methodology	to	Quantify	the	Effects	of	Access	Management	on	Roadway	Operations	and	Safety,	3	volumes,

prepared	by	the	University	of	South	Florida	for	the	Florida	Department	of	Transportation,	2001.	(http://www.accessmanagement.info/Document/methodology-quantify-effects-access-management-roadway-operations-and-safety) 

16	 AASHTO,	Highway	Safety	Manual,	Washington,	DC,	2010.	(http://www.highwaysafetymanual.org/) 

17 AASHTO, Highway Safety Manual, Washington, DC, 2010. (http://www.highwaysafetymanual.org/). 

18 TRB, Access Management Manual, Washington, DC, 2003 (http://www.trb.org/Publications/AMM14.aspx) 

19 FHWA, Safe Access is Good for Business. (http://ops.fhwa.dot.gov/publications/amprimer/access_mgmt_primer.htm) 

20	 Hallmark,	S.,	et	al.	(http://www.intrans.iastate.edu/reports/safety_ops_air.pdf) 

21 Eisele, W.L., and W.E. Frawley. Estimating the Safety and Operational Impact of Raised Medians and Driveway Density: 

Experiences	from	Texas	and	Oklahoma	Case	Studies,	Transportation	Research	Record	1931,	2005.	(https://trid.trb.org/ 

view/778678) 

22	 Hallmark,	S.,	et	al.	(http://www.intrans.iastate.edu/reports/safety_ops_air.pdf) 

23 FHWA, Access Management in the Vicinity of Intersections - Technical Summary, FHWA-SA-10-002, Washington, DC. (https:// 

safety.fhwa.dot.gov/intersection/other_topics/fhwasa10002/) 

24	 FHWA,	Bicycle	Road	Safety	Audit	Guidelines	and	Prompt	Lists,	FHWA_SA_12_018,	Washington,	DC,	May	2012.	(http://safety. 

fhwa.dot.gov/ped_bike/tools_solve/fhwasa12018/) 

25 TRB, Highway Capacity Manual (HCM 2010), Washington, DC, 2010. (http://www.trb.org/Main/Blurbs/175169.aspx) 

26	 Ibid.

27	 Stamatiadis,	N.,	et	al.	(http://transportation.ky.gov/Congestion-Toolbox/Documents/KTC%20Access%20Management%20

Report.pdf) 

28 TxDOT, Access Management Manual, 2011. (http://onlinemanuals.txdot.gov/txdotmanuals/acm/acm.pdf) 

29	 APWA,	“Town	of	LeRay	Commercial	Corridor	Planning,”	APWA	Reporter,	Washington,	June	2011.	(http://www.apwa.net/ 

Resources/Reporter/Articles/2011/6/Town-of-LeRay-commercial-corridor-planning) 

30	 Kirk,	A.,	et	al.	Quantification	of	the	Benefits	of	Access	Management	for	Kentucky,	Research	Report	KTC-06-16	/	SPR290-05-

1F,	Kentucky	Transportation	Center,	July	2006.	(https://uknowledge.uky.edu/cgi/viewcontent.cgi?article=1118&context=ktc_researchreports) 

31 CTRE,	Access	Management	Awareness	Program.	(http://www.ctre.iastate.edu/research/access/phaseii/whole_report.pdf) 

20
32 Arinello, A. Are Roundabouts Good for Business?, Denver, CO, 2004. (https://www.cityofgolden.net/media/roundaboutpaper.pdf) 

33 TRB, Evaluating Alternative Operations Strategies to Improve Travel Time Reliability, Washington, DC 2011. (http://www.trb. 

org/Main/Blurbs/168142.aspx) 

34 TRB, Evaluating the Performance of Corridors with Roundabouts, NCHRP Report 772, Washington, DC, 2014. (http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_772.pdf) 

35 Wilmington Metropolitan Planning Organization (WMPO), Public Involvement Policy, 2009. (http://www.wmpo.org/ 

PDF/2009-09_WMPO_Policy_PublicInvolvement.pdf)25 

36 WMPO, Memorandum of Understanding for Cooperative, Comprehensive, and Continuing Transportation Planning, 2006. 

(http://www.wmpo.org/PDF/2006_WMPO_MOU.pdf) 

37 IowaDOT, Access Management Report, Ames, IA, 2014. (http://www.iowadot.gov/traffic/manuals/tsmanual.htm) 

38 APWA (http://www.apwa.net/Resources/Reporter/Articles/2011/6/Town-of-LeRay-commercial-corridor-planning) 

39 Teach America, Corridor Visualization Explorer. (http://teachamerica.com/CVE/) 

40 Ibid. 

21
Additional references 

Access Management in the Vicinity of Intersections Technical Summary (http://safety.fhwa. 

dot.gov/intersection/resources/fhwasa10002/) 

Access Management Principles (http://ops.fhwa.dot.gov/access_mgmt/presentations/am_ 

principles_intro/index.htm) 

Transportation Research Board Access Management Web site (http://www.accessmanagement.info/) 

Guidebook for Incorporating Access Management in Transportation Planning (NCHRP Report 

548) (http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_548.pdf) 

Highway Safety Manual, American Association of State Highway and Transportation Officials

(http://www.highwaysafetymanual.org/Pages/default.aspx) 

Crash Modification Factor (CMF) Clearinghouse [quick search “access management”]

(http://www.cmfclearinghouse.org/) 

Guide for the Geometric Design of Driveways (NCHRP Report 659) (http://onlinepubs.trb.org/ 

onlinepubs/nchrp/nchrp_rpt_659.pdf) 

Florida Department of Transportation Median Handbook (https://fdotwww.blob.core.windows.net/sitefinity/docs/default-source/planning/systems/sm/accman/fdot-medianhandbook-sept-2014-edits-10-25-2017.pdf?sfvrsn=401841d5_2) 

Left-Turn Accommodations at Unsignalized Intersections (NCHRP Report 745) 

(http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_745.pdf) 

Design Guidance for Intersection Auxiliary Lanes (NCHRP Report 780) 

(http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_780.pdf) 

22

FHWA-SA-15-005

FOR MORE INFORMATION

Office of Safety: Jeffrey Shaw, jeffrey.shaw@dot.gov

Office of Operations: Mark Doctor, mark.doctor@dot.gov

FHWA Resource Center: David Engstrom, david.engstrom@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

Updated July 2020