Efficient Use of Highway Capacity 

Summary

Report to Congress

November 2010
Foreword 

This report was developed to summarize the implementation of safety shoulders as travel lanes as a 

method to increase the efficient use of highway capacity. Its purpose is to provide a succinct 

overview of efforts to use left or right shoulder lanes as temporary or interim travel lanes. As part 

of this summary, information related to the impact of that shoulder usage on highway safety and/or 

accidents during operations was reviewed as well. The intent of the report is to provide critical 

information that the Federal Highway Administration (FHWA) can use to formulate guidance for 

transportation agencies on providing temporary shoulder use as a means of increasing roadway 

capacity. The study that generated this product was conducted at the request of Congress through 

the Safe, Accountable, Flexible, Efficient Transportation Equity Act, A Legacy for Users Technical 

Corrections Act of 2008 (2008 Technical Corrections Act). Those issues that need to be considered 

include design, traffic control devices, performance measures, potential safety benefits, maintenance 

concerns, enforcement roles and processes, incident response, training for personnel, costs, liability 

and legal issues, and public outreach and education. Careful consideration of these issues can help 

ensure a shoulder use deployment is effective without having negative impacts on safety and 

operations. 

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. 

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' 

names appear in this report only because they are considered essential to the objective of the 

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. The FHWA periodically reviews quality issues and adjusts its programs and processes 

to ensure continuous quality improvement. 

Technical Report Documentation Page

1. Report No.

FHWA-HOP-10-023

2. Government Accession No. 3. Recipient's Catalog No.

4. Title and Subtitle

EFFICIENT USE OF HIGHWAY CAPACITY SUMMARY

5. Report Date

May 2010

6. Performing Organization Code

HOP

7. Author(s)

Beverly Kuhn

8. Performing Organization Report No.

Report

9. Performing Organization Name and Address

Texas Transportation Institute

The Texas A&M University System

College Station, Texas 77843-3135

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

Project No. DTFH61-06-D-00007

12. Sponsoring Agency Name and Address

U.S. Department of Transportation

Federal Highway Administration

Office of Operations (HOP)

Mail Stop: E86-205

1200 New Jersey Avenue, SE

Washington, DC 20590

13. Type of Report and Period Covered

Technical

14. Sponsoring Agency Code

FHWA

15. Supplementary Notes

Project performed in cooperation with the U.S. Department of Transportation, Federal Highway 

Administration.

Project Title: Efficient Use of Highway Capacity Summary

16. Abstract

This report was developed to summarize the implementation of safety shoulders as travel lanes 

as a method to increase the efficient use of highway capacity. Its purpose is to provide a succinct 

overview of efforts to use left or right shoulder lanes as temporary or interim travel lanes. As 

part of this summary, information related to the impact of that shoulder usage on highway safety 

and/or accidents during operations was reviewed as well. The intent of the report is to provide 

critical information that the Federal Highway Administration (FHWA) can use to formulate 

guidance for agencies on providing temporary shoulder use as a means of increasing roadway 

capacity. The study that generated this product was conducted at the request of Congress

through the 2008 Technical Corrections Act. Those issues that need to be considered include 

design, traffic control devices, performance measures, potential safety benefits, maintenance 

concerns, enforcement roles and processes, incident response, training for personnel, costs, 

liability and legal issues, and public outreach and education. Careful consideration of these issues 

can help ensure a shoulder use deployment is effective without having negative impacts on safety 

and operations.

17. Key Words

Highway capacity, safety shoulder, temporary 

shoulder use, safety, operations, managed 

lanes, HOT lanes, HOV lanes, geometric design, 

active traffic management

18. Distribution Statement

No restrictions. This document is available to 

the public through the FHWA Freeway 

Management Program website:

http://ops.fhwa.dot.gov/freewaymgmt/mngd_

lns_hov.htm

19. Security Classif.(of this report)

Unclassified

20. Security Classif. (of 

this page)

Unclassified

21. No. of 

Pages

96

22. Price

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized
i

Table of Contents

Executive Summary ........................................................................................................ 1

Chapter 1: Background .................................................................................................. 7

Scope and Purpose ..................................................................................................... 7

Document Overview .................................................................................................... 7

Intended Audiences and Uses..................................................................................... 7

The Planning Framework and Shoulder Use............................................................... 8

The Transportation Plan............................................................................................ 8

The Transportation Improvement Program ............................................................... 8

Planning Process Elements ...................................................................................... 9

Developing the Transportation Plan with Shoulder Use in Mind................................ 9

Project Design......................................................................................................... 12

Chapter Summary ..................................................................................................... 13

Chapter 2: Context and Findings.................................................................................. 15

Congestion Management and Mitigation ................................................................... 15

Managed Lanes ...................................................................................................... 16

Active Traffic Management...................................................................................... 17

Shoulder Use—The European Experience................................................................ 17

Plus Lane ................................................................................................................ 19

Junction Control ...................................................................................................... 20

Shoulder Lanes—The American Experience............................................................. 21

Bus on Shoulders.................................................................................................... 22

Dedicated Shoulder Lanes...................................................................................... 25

Priced Dynamic Shoulder Lanes............................................................................. 29

Hurricane Evacuation Routes.................................................................................... 31

Complementary ATM Strategies................................................................................ 31

Speed Harmonization.............................................................................................. 31

Junction Control ...................................................................................................... 32

Chapter Summary ..................................................................................................... 32

Chapter 3: Critical Issues ............................................................................................. 35

Design ....................................................................................................................... 35

Treatment at Interchanges ...................................................................................... 36

Drainage.................................................................................................................. 37

Emergency Refuge Areas ....................................................................................... 37

Rumble Strips.......................................................................................................... 37

Safety Studies......................................................................................................... 38

ITS Components ..................................................................................................... 38

Traffic Control Devices .............................................................................................. 38

Pavement Markings................................................................................................... 43

Performance.............................................................................................................. 43

Operations............................................................................................................... 43

Safety...................................................................................................................... 45

Maintenance.............................................................................................................. 46
ii

Enforcement .............................................................................................................. 46

Incident Response..................................................................................................... 46

Training...................................................................................................................... 47

Costs ......................................................................................................................... 47

Liability Issues ........................................................................................................... 47

Legal Issues .............................................................................................................. 48

Public Outreach and Education ................................................................................. 48

NCHRP/AASHTO/FHWA Domestic Scan.................................................................. 48

Chapter Summary ..................................................................................................... 49

Chapter 4: Case Studies .............................................................................................. 50

Case Study: The Netherlands—Temporary Shoulder Use and Speed Harmonization

.................................................................................................................................. 50

Overview ................................................................................................................. 50

Project Conceptualization........................................................................................ 53

Facility Management ............................................................................................... 53

Technologies Deployed........................................................................................... 53

Performance of System........................................................................................... 54

Case Study: Germany—Temporary Hard Shoulder Use and Speed Harmonization . 55

Overview ................................................................................................................. 55

Project Conceptualization........................................................................................ 59

Facility Management ............................................................................................... 60

Technologies Deployed........................................................................................... 60

Performance of System........................................................................................... 60

Case Study: Great Britain—Temporary Shoulder Use System.................................. 62

Overview ................................................................................................................. 62

Project Conceptualization........................................................................................ 65

Facility Management ............................................................................................... 65

Technologies Deployed........................................................................................... 66

Performance of System........................................................................................... 66

Case Study: Virginia—I-66 Temporary Shoulder and HOV Lanes ............................ 67

Overview ................................................................................................................. 67

Project Conceptualization........................................................................................ 71

Facility Management ............................................................................................... 71

Performance of System........................................................................................... 72

Case Study: Minnesota—Priced Dynamic Shoulder Lanes....................................... 72

Overview ................................................................................................................. 72

Project Conceptualization........................................................................................ 74

Facility Management ............................................................................................... 74

Technologies Deployed........................................................................................... 74

Performance of System........................................................................................... 74

Case Study: Massachusetts—Shoulder Lane Use .................................................... 74

Overview ................................................................................................................. 74

Project Conceptualization........................................................................................ 76

Facility Management ............................................................................................... 76

Technologies Deployed........................................................................................... 77

Performance of System........................................................................................... 77

Case Study: Washington—State Route 2, Temporary Shoulder Use........................ 77
iii

Overview ................................................................................................................. 77

Project Conceptualization........................................................................................ 78

Facility Management ............................................................................................... 78

Technologies Deployed........................................................................................... 80

Performance of System........................................................................................... 80

Chapter 5: Final Remarks ............................................................................................ 80

Acknowledgements ....................................................................................................... 83

Bibliography .................................................................................................................. 84

Appendix A: Interview Questions for Agency Representatives..................................... 89

Contact Information....................................................................................................... 91
iv

List of Figures

Figure 1. Flowchart. Developing the Transportation Plan [Adapted from ( 4). ...........................................11

Figure 2. Flowchart. The Regional Context and Shoulder Use..........................................................................12

Figure 3. Graph. Causes of Congestion in the United States. ( 8)........................................................................15

Figure 4. Graph. Lane Management Operational Strategies. ( 9) .......................................................................16

Figure 5. Photo. Temporary Shoulder Use—Germany ( 13). ................................................................................18

Figure 6. Photo. Shoulder Use with Emergency Refuge Area—England. ( 1)...............................................19

Figure 7. Photo. Plus Lane—The Netherlands. ( 1)..................................................................................................20

Figure 8. Graphic. Junction Control Schematic in Germany. ( 16) ......................................................................20

Figure 9. Photo. Bus on Shoulders—Mn/DOT (Photo courtesy of Mn/DOT).............................................23

Figure 10. Photo. Converted Shoulders on I-5—California (Photo Courtesy of CALTRANS). .............26

Figure 11. Photo. I-66 HOV/Shoulder Lane Adaptation—Virginia (Photo Courtesy of VDOT)..........27

Figure 12. Graphic. Open Priced Dynamic Shoulder Lane—Minneapolis, Minnesota. ( 27) ...................29

Figure 13. Graphic. Closing Priced Dynamic Shoulder Lane—Minneapolis, Minnesota. ( 27) ...............30

Figure 14. Graphic. Closed Priced Dynamic Shoulder Lane—Minneapolis, Minnesota. ( 27).................30

Figure 15. Photo. Speed Harmonization—The Netherlands. ............................................................................32

Figure 16. Photo. I-66 Regulatory Sign with Lane Control Signals (Photo Courtesy of VDOT). .........39

Figure 17. Photo. I-66 Hours of Use Regulatory Sign (Photo Courtesy of VDOT).....................................39

Figure 18. Photo. VDOT I-66 Regulatory Signs (Photo Courtesy of VDOT).................................................40

Figure 19. Photo. Mn/DOT BOS Regulatory Sign (Photo Courtesy of Mn/DOT).......................................41

Figure 20. Graphic. Mn/DOT BOS Warning Sign (Image Courtesy of Mn/DOT). ......................................41

Figure 21. Photo. Regulatory Shoulder Use Signs (Photo Courtesy of MassDOT). ( 23) ...........................42

Figure 22. Photo. Warning Shoulder Use Sign (Photo Courtesy of MassDOT). ( 23)................................. 42

Figure 23. Drawing. Shoulder Use Regulatory Sign (Drawing Courtesy of WSDOT). ( 26)......................43

Figure 24. Photo. Temporary Right Shoulder Use—The Netherlands. ( 36)..................................................51

Figure 25. Photo. Plus Lane in The Netherlands. ( 36)............................................................................................51

Figure 26. Photo. Speed Harmonization—The Netherlands. ............................................................................52

Figure 27. Graph. Incident Reductions with Temporary Shoulder Use—The Netherlands. ( 14) ........54

Figure 28. Photo. Right Shoulder Use with Speed Harmonization—Germany. ( 13) ................................. 56

Figure 29. Illustration. Temporary Hard Shoulder Use Signs—Germany. ( 13)...........................................57

Figure 30. Illustration. Signs and Markings for Temporary Hard Shoulder Use Continuation 

through Interchange—Germany. ( 13) ............................................................................................................................57

Figure 31. Photo. Continuation of Temporary Hard Shoulder Use through an Interchange—

Germany. ( 13)............................................................................................................................................................................58

Figure 32. Illustration. Signs and Markings for Temporary Hard Shoulder Use Termination at 

Interchange—Germany. ( 13)..............................................................................................................................................58

Figure 33. Photo. Termination of Temporary Hard Shoulder Use at Interchange—Germany. ( 13)..59

Figure 34. Graph. Speed-Volume Relationship of Temporary Shoulder Use—Germany. ( 13)..............61

Figure 35. Graph. Flow Impacts of Speed Harmonization—Germany. ( 41)..................................................61

Figure 36. Graph. Safety Benefits of Speed Harmonization—Germany. ( 40)...............................................62

Figure 37. Photo. Emergency Refuge Area on Facility with Active Traffic Management—England.64

Figure 38. Photo. Emergency Call Box on Facility with Active Traffic Management—England.........64

Figure 39. Photo. I-66 Peak Period Shoulder Use—Virginia ( 50). .....................................................................68
v

Figure 40. Photo. I-66 HOV Lanes, West of HOV/SL Portion—Virginia ( 50). ...............................................69

Figure 41. Photo. I-66 HOV/SL Portion—Virginia ( 50). ........................................................................................69

Figure 42. Illustration. I-66 HOV/SL Lane Plan View—Virginia ( 50). .............................................................70

Figure 43. Illustration. I-66 HOV/SL Typical Cross-Section—Virginia ( 50). .................................................70

Figure 44. Photo. I-495, Viewing Dual Entrance Ramps from I-66—Virginia. ..........................................71

Figure 45. Illustration. PDSL on I-35W—Minneapolis, Minnesota. ( 27) ........................................................73

Figure 46. Photo. Breakdown Shoulder Use on I-93—Massachusetts. ( 23) .................................................76

Figure 47. Photo. US 2 Shoulder Use—Everett, Washington. ( 55)....................................................................78

Figure 48. Illustration. US 2 Trestle Original Cross-Section—Everett, Washington. ( 55).......................79

Figure 49. Illustration. US 2 Cross-Section for Shoulder Use—Everett, Washington. ( 55).....................79

List of Tables

Table 1. Shoulder Use Installation Costs—Mn/DOT. ( 18) .....................................................................................48
1

Executive Summary

Chapter 1: Background

This report was developed to summarize the implementation of safety shoulders as travel lanes as a 

method to increase the efficient use of highway capacity. Its purpose is to provide a succinct 

overview of efforts to use left or right shoulder lanes as temporary or interim travel lanes. As part 

of this summary, information related to the impact of that shoulder usage on highway safety and/or 

accidents during operations was reviewed as well. The intent of the report is to provide critical 

information that the Federal Highway Administration (FHWA) can use to formulate guidance for 

transportation agencies on providing temporary shoulder use as a means of increasing roadway 

capacity. The study that resulted in this report was conducted at the request of Congress in the 2008 

Technical Corrections Act. The issues that need to be considered include design, traffic control 

devices, performance measures, potential safety benefits, maintenance concerns, enforcement roles 

and processes, incident response, training for personnel, costs, liability and legal issues, and public 

outreach and education. Careful consideration of these issues can help ensure a shoulder use 

deployment is effective without having negative impacts on safety and operations.

Document Overview

This document is divided into five chapters that discuss in detail the results of the study and the 

critical issues and findings related to the use of shoulders for increasing capacity during congested 

travel periods. The titles of each chapter and major topics covered are highlighted below. 

• Chapter One—Background: Provides an overview of the document including its scope 

and purpose, intended audiences and uses, and background information on the roles 

that planning and project development play in the decision to use a shoulder as a travel 

way to increase capacity and enhance mobility.

• Chapter Two—Context and Findings: Discusses the concept of shoulder use within 

the context of active traffic management (ATM) and summarizes the domestic and 

foreign experience with this operational strategy and those that are complementary to 

its deployment.

• Chapter Three—Critical Issues: Gives a brief overview of the critical issues that need 

to be addressed when considering the use of shoulders for temporary capacity increase 

on congested freeways. 

• Chapter Four—Case Studies: Provides case studies of European and domestic 

applications of shoulder use. 

• Chapter Five—Final Remarks: Includes final remarks related to the document and its 

use and provides a complete list of references used in the development of this 

document.
2

Chapter 2: Context and Findings

The report documents usage of shoulders as travel lanes in both the United States and three 

European countries. 

Shoulder Lanes—The American Experience

In the United States, the primary use of shoulders has been as a safety refuge area. The limited 

shoulder use as a travel lane has been primarily reserved for special users of the roadway system, 

most often transit vehicles. Some shoulder use dates back to the 1970s, and many installations 

have been in operation for more than 10 years to address congestion on urban corridors. Agencies 

have seen bus use of shoulders as a low-cost and quick strategy to improve bus operations and 

reliability without having to acquire additional right-of-way and invest additional large sums of 

money into the infrastructure. The length of these deployments varies depending on location, 

ranging from a more than 290-mile comprehensive network in the Minneapolis-St. Paul 

metropolitan area to deployments less than 1 mile in length used to serve as a queue jump for 

transit in Delaware. The operational strategies often depend on the congestion on the general 

purpose lanes and often require speed restrictions of the transit vehicles using the shoulders. 

Overall, experience using shoulders for interim use has been positive in the United States, and more 

agencies are considering the strategy to address growing congestion on their urban freeway 

networks. In fact, several States have deployed temporary shoulder use for all vehicles on 

congested corridors with success. Another application that is much more difficult to research and 

document is the number of locations where an existing shoulder has been narrowed or taken away 

to allow for widening with an extra permanent travel lane. This method is more commonly used in 

roadway work zones to maintain the existing number of travel lanes during construction. However, 

it has been applied in some permanent forms as well. In the United States, usage can be broken out 

into the following categories:

- Bus-only use on shoulders

- Converted shoulders used as permanent lanes

- Temporary use of shoulders for either general purpose traffic or managed lanes

- Emergency (Hurricane) Evacuation Routes

Shoulder Use—The European Experience

In Europe, part-time shoulder use is a congestion management strategy typically deployed in 

conjunction with complementary traffic management strategies – such as variable speed limits 

(speed harmonization) and/or ramp metering – to address capacity bottlenecks on the freeway 

network. European implementers include The Netherlands, Germany, and Great Britain. The 

strategy provides additional vehicle-moving capacity during times of congestion and reduced travel 

speeds. The use of the exterior shoulder during peak travel periods has been used in Germany 

since the 1990s. When travel speeds are reduced, dynamic signs over or next to the shoulder 

indicate that travel on the shoulder is permitted. 

A complete series of traffic signs indicate operations related to temporary shoulder use, including 

one with a supplemental speed limit indication (used when overhead gantries are not present). 
3

These signs and the overhead lane messages are blank when travel on the shoulder is not 

permitted. Temporary shoulder use is permitted only when speed harmonization is active and 

speed limits are reduced, thus providing an operating environment only when speeds are managed 

below posted levels. 

Generally, implementation of temporary shoulder use is at the discretion of the traffic management 

center operator, although traffic volumes help determine the need for the strategy. A typical 

installation in Europe incorporates a number of unique roadway features, which can include: 

• Lightweight gantries.

• Lane control signals.

• Dynamic speed limit signals.

• Dynamic message signs.

• Automated enforcement technology.

• Closed-circuit television cameras.

• Enhanced lighting.

• Roadway sensors.

• Emergency roadside telephones.

• Advanced incident detection.

• Intensified incident management.

• Emergency refuge areas or pull-outs beyond the shoulder. 

Operation of the system is handled by the regional control center, with operators on hand to 

monitor the system and initiate the modified operations as necessary. Specifically, operators use 

closed-circuit television cameras (CCTVs) mounted on lightweight sign gantries or separately to 

check for incidents and stalled vehicles in the shoulder before activating the system. 

Chapter 3: Critical Issues

The primary concern related to shoulder use involves its impact on operations and safety. The 

purpose of this project was to assess the deployments of shoulder use in the United States and 

determine the impacts on, the experience with, and the addressing of the following safety issues:

• Conflicts at access ramps.

• Sight distance.

• Conflicts with motorists pulling onto the shoulder for emergency purposes.

• Loss of use of the shoulder for emergency refuge.

• Need for bus driver training.

• Speed differential between the general purpose lanes and the shoulder.

• Effect on general purpose lane users.

• Return merge distance adequacy.

• Debris hazards on shoulder.
4

• Reduced bridge clearance.

• Drainage.

• Operational efficiency.

• Crash experience.

By providing a summary of this information and data related to shoulder use experience, it is 

expected that the project can assist FHWA with developing guidance on the subject and identifying 

what, if any, research needs to be conducted to address unknowns related to the operational 

strategy and its potential long-term and widespread use in the United States.

Agencies need to consider a wide range of issues when determining whether shoulder use is 

appropriate for a particular corridor or region. Experience both overseas and domestically 

provides a wealth of experience from which agencies can learn to make informed decisions. From 

the European perspective, part-time shoulder use is only used during congested periods when 

queues begin to build at bottlenecks in the system. Moreover, this treatment is almost always 

deployed in conjunction with speed harmonization. The intent is to reduce the speeds along the 

corridor and smooth out driver performance and reduce the likelihood of collisions. (1)

Furthermore, European agencies have realized both safety and mobility benefits as a result of these 

projects. While American deployments have been limited, the experience has generally been 

positive. However, safety benefits have not been conclusive. The issues that need to be considered 

include design, traffic control devices, performance measures, potential safety benefits, 

maintenance concerns, enforcement roles and processes, incident response, training for personnel, 

costs, liability and legal issues, and public outreach and education. Careful consideration of these 

issues can help ensure a shoulder use deployment is effective without having negative impacts on 

safety and operations.

Another area needing further analysis is the topic of left shoulder use versus right shoulder use. 

Domestically, almost all applications of part-time shoulder use have occurred on the right side, 

while shoulder conversions to permanent lanes have tended to be more prominent on the left side. 

Each application has a different subset of design and operational considerations to analyze.

Chapter 4: Case Studies 

Detailed Case Study reviews were made of the following locations:

- The Netherlands

- Germany

- Great Britain

- Virginia

- Minnesota

- Massachusetts

- Washington
5

Chapter 5: Final Remarks

This report was developed to summarize the implementation of safety shoulders as travel lanes as a 

method to increase the efficient use of highway capacity. Its purpose is to provide a succinct 

overview of efforts to use left or right shoulder lanes as temporary or interim travel lanes. As part 

of this summary, information related to the impact of shoulder usage on highway safety and/or 

accidents during operations was reviewed as well. The report provides critical information that the 

FHWA can use to formulate guidance for agencies on providing temporary shoulder use as a means 

of increasing roadway capacity. The study that resulted in this report was conducted at the request 

of Congress in the 2008 Technical Corrections Act. 

Agencies need to consider a wide range of issues when determining whether shoulder use is 

appropriate for a particular corridor or region. Experience both overseas and domestically 

provides a wealth of experience from which agencies can learn to make informed decisions. From 

the European perspective, temporary shoulder use is only used during congested periods when 

queues begin to build at bottlenecks in the system. Moreover, this treatment is almost always 

deployed in conjunction with dynamic lane control signing and speed harmonization. Furthermore, 

European agencies have realized both safety and mobility benefits as a result of these projects. 

While American deployments have been limited, experience has been positive, though safety 

benefits have not been conclusive. The issues that need to be considered include design—such as 

the treatment at interchanges and auxiliary lanes, drainage, emergency refuge areas, rumble strips, 

and Intelligent Transportation Systems (ITS) components; traffic control devices; and operational 

and safety performance measures. In addition, maintenance concerns, enforcement roles and 

responsibilities, incident response procedures, personnel training, costs, liability and legal issues, 

and public outreach and education are issues that should be examined. Careful consideration of 

these issues can help ensure that a shoulder use deployment is effective without having negative 

impacts on safety and operations. 

The following results can be taken away from this summary:

• The use of buses on shoulders has generally significantly benefited transit trip time 

reliability in those corridors where it has been implemented.

• There have been shoulder use projects that have shown bottleneck relief at spot 

locations.

• Incident data provided from the U.S. seems to be inconclusive at this point. There are 

safety benefits provided from the European applications. However, the shoulder use is 

only a part of a much larger investment in ATM technology and resources to manage 

them.

• There have been longer incident clearance times in areas that don’t have shoulders 

available to move incidents off the highway. Also, responders don’t have the benefit of 

traveling the shoulder to reach the incident scene.

• European usage of hard shoulder running has always been accompanied by additional 

ATM strategies such as dynamic lane control signals and variable speed limits. These 

additional support strategies have generally been lacking in U.S. applications.
6

As a result of the information gained from this study, consideration should be given to the 

following:

• The FHWA should consider developing clearer agency guidance on the use of shoulders. 

This would need to be a joint effort from the Offices of Infrastructure (Design), Safety, 

and Operations (including how the Manual on Uniform Traffic Control Devices (MUTCD)

relates to shoulder use lanes). The lack of existing U.S. performance data would also 

point to the need for more research in this area.

• Hard shoulder running was one of the ATM strategies recommended for 

implementation in the U.S. from a recent international scan. As FHWA and American 

Association of State Highway and Transportation (AASHTO) develop guidance on ATM, 

they should clarify guidance on temporary shoulder usage. This would include

comparing the differences in current U.S. usage to that of the European countries.

• Research and modeling for temporary shoulder use is lacking at this time. This could be 

covered in research being developed for the ATM program. 

• The results of the NCHRP/AASHTO/FHWA Domestic Scan on Maximizing Flow on 

Existing Highway Facilities should be considered in the development of shoulder use 

guidance 
7

Chapter 1: Background

Scope and Purpose

This report was developed to summarize the implementation of safety shoulders as travel lanes as a 

method to more effectively use existing highway capacity. Its purpose is to provide a succinct 

overview of efforts to use left or right shoulder lanes as temporary or interim travel lanes. As part 

of this summary, information related to the impact of that shoulder usage on highway safety and/or 

accidents during operations was reviewed as well. The intent of the report is to provide critical 

information that the Federal Highway Administration (FHWA) can use to formulate guidance for 

agencies on providing temporary shoulder use as a means of increasing roadway capacity. The 

study that resulted in this report was conducted at the request of Congress through the 2008 

Technical Corrections Act.

Document Overview

This document is divided into five chapters that discuss in detail the results of the study and the 

critical issues and findings related to the use of shoulders for increasing capacity during congested 

travel periods. The titles of each chapter and major topics covered are highlighted below. 

• Chapter One—Background: Provides an overview of the document including its scope 

and purpose, intended audiences and uses, and background information on the roles 

that planning and project development play in the decision to use a shoulder as a travel 

way to increase capacity and enhance mobility.

• Chapter Two—Context and Findings: Discusses the concept of shoulder use within 

the context of active traffic management (ATM) and summarizes the domestic and 

foreign experience with this operational strategy and those that are complementary to 

its deployment.

• Chapter Three—Critical Issues: Gives a brief overview of the critical issues that need 

to be addressed when considering the use of shoulders for temporary capacity increase 

on congested freeways. 

• Chapter Four—Case Studies: Provides case studies of European and domestic 

applications of shoulder use. 

• Chapter Five—Final Remarks: Includes final remarks related to the document and its 

use and provides a complete list of references used in the development of this 

document.

Intended Audiences and Uses

The intended audience for this report is transportation professionals and agencies at the State, 

regional, and local levels involved in transportation planning, project development, and operations 

who may be considering the temporary use of a highway shoulder to increase capacity on a 

congested facility, be it for special users or general purpose traffic. It is anticipated that the 

information provided in this document will offer valuable insight for professionals and ensure that 

they carefully consider all aspects of shoulder use from the planning, design, operational, and safety 

perspectives prior to implementation. Moreover, agencies might factor potential shoulder use into 
8

the planning process as a potential operational strategy where capacity increases are limited. The 

report will also lay the groundwork for supporting project development efforts once the planning 

process is complete. 

The Planning Framework and Shoulder Use

As modified and enhanced by the Intermodal Surface Transportation Efficiency Act of 1991 

(ISTEA), the modern transportation planning process works to improve the transportation system 

and investment decision making associated with transportation projects. (2) Based on the paradigm 

shift from construction to system preservation, ISTEA identified critical issues related to 

transportation planning, including but not limited to:

• Linking transportation to the economic, mobility, and accessibility needs of the country.

• Emphasizing the participation of key stakeholders in the transportation planning 

process.

• Recognizing the constraints limiting expansion.

• Protecting the human and natural environments while providing accessibility to 

transportation services.

• Linking transportation planning to the air quality objectives in the Clean Air Act 

amendments and State air quality plans. (3) 

The Transportation Plan

The transportation plan (also known as the long-range transportation plan, metropolitan 

transportation plan, regional transportation plan, etc.) is a statement of the way in which the region 

plans to invest in the transportation system. (4) This 20-year document, which must be updated on 

a periodic basis (typically every 5 years, but every 3 years for nonattainment and maintenance 

areas), sets the stage for transportation investment in the region by mapping general strategies for 

improving the safe and efficient movement of people and goods throughout the area. Operational 

strategies, which might include temporary use of shoulders during peak periods or measures such 

as managed lanes, can be part of this plan.

The Transportation Improvement Program

The transportation improvement program (TIP) is a short-range document related to the 

transportation plan. Covering a minimum 3-year period of investment, this fiscally constrained 

document identifies the immediate high-priority projects and strategies as outlined in the 

transportation plan and advances them for implementation. (4) In short, the Metropolitan Planning 

Organization (MPO) takes those projects in the transportation plan and lays out which of them can 

realistically be undertaken with the limited resources available over the next several years. The TIP 

is incorporated into the statewide transportation improvement program (STIP) and must conform 

to the state implementation plan (SIP) for improving air quality for projects to move forward to 

implementation. 
9

Planning Process Elements

The elements of the metropolitan transportation planning process include public involvement, 

planning factors, management systems input, major investment studies (MIS), the air quality 

conformity process, and the financial plan. Ways in which temporary shoulder use for capacity 

increases and other operational strategies may impact these elements are as follows: 

• Public involvement when planning operational improvements helps ensure that all of 

the social, economic, and environmental consequences of investment decisions are 

considered and that the MPO has the broad support of the community. 

• The goals and objectives of various operational strategies easily fit within the general 

planning factors in the transportation planning process. 

• Congestion management systems might consider shoulder operational strategies, whose 

goals and objectives work in concert with the system, to maximize the efficiency 

potential for the transportation network. 

• Incorporating shoulder use operational strategies as potential solutions in the major 

investment study can help address the factors influencing project solutions while 

efficiently and effectively meeting the needs of the community. 

• Shoulder use strategies that involve pricing may present transportation agencies with 

an opportunity to capitalize on innovative techniques to balance financing with regional 

goals. 

Developing the Transportation Plan with Shoulder Use in Mind

Figure 1 and 2 outline the basic steps in the general planning process and the Transportation 

Improvement Plan process. These figures indicate where the critical consideration of operational 

strategies such as temporary shoulder use fits into the process. Regional planning and corridorand facility-level planning through the MIS process are all part of developing the 20-year regional 

transportation plan. Once projects get placed on the TIP and the STIP, they move to 

implementation. It is important to note that the MPO, FHWA, and the Federal Transit 

Administration (FTA) check for conformity with the SIP at the plan, TIP, and project levels. Once 

again, public involvement throughout the entire planning process cannot be overlooked. It helps an 

MPO develop a comprehensive plan for transportation improvements that is responsive to the 

community and its needs. 

Incorporating shoulder use for capacity increases into the planning process requires agencies to 

consider various planning-related issues from a slightly different perspective. While all of the 

planning considerations listed below are general transportation factors that can apply to virtually 

any mode, they are listed here within the shoulder use context. Throughout the entire planning 

process, the MPO should consider these issues when assessing shoulder use strategies as potential 

solutions to the region’s transportation needs and when formulating the plan and TIP. The typical 

shoulder use planning considerations include but are not limited to the following:

• Geometric design and cross-section.

• Decision making needs and traffic-control devices.
10

• Enforcement.

• Environmental justice.

• Evaluation and monitoring.

• Funding and financing.

• Incident management.

• Maintenance.

• Interoperability and technology components.

• Public outreach and education.

• Legal and institutional challenges.

• Operational flexibility.

• Pricing as an option.
11

Figure 1. Flowchart. Developing the Transportation Plan (4)

In many areas temporary use of shoulders has been implemented as a low-cost interim solution. 

Whereas the ultimate plan is a much more costly widening project or reconstruction, given the need 

to develop transportation plans that are fiscally constrained, there might be more opportunities for 

operational-based, lower-cost projects in the near term.

One area that is lacking is historical data for use in traditional planning models. To that extent, 

additional modeling and research efforts are needed to fill this gap in data.
12

Figure 2. Flowchart. The Regional Context and Shoulder Use.

Project Design

During project design, agencies must engage in even more detailed planning and design to ensure 

that all aspects of shoulder use operational strategies are considered and assessed for a particular 

facility. Design standards dictate project design. By their very nature, temporary shoulder usage 

projects run contrary to most design standards for highways since they have a requirement for 

shoulders. Therefore, almost any project proposing to use the shoulder as a travel lane is going to 

involve a design exception. These design exceptions will need to be analyzed on a case-by-case 

basis with particular emphasis given to the safety elements of the roadway. This will involve 
13

geometric design elements of the roadway, traffic volumes and congestion, and crash history. 

Careful consideration of these issues at the facility level can help ensure that the shoulder use 

operational strategy is effective in meeting the goals and objectives for the corridor, enhance 

operational flexibility, and optimize use over the life of the project. These parameters include but 

are not limited to the following:

• Design vehicle.

• Design speed.

• Access control, design, and spacing.

• Signing and pavement markings.

• Driver information.

• Safety.

• Acceleration and deceleration distance.

• Vertical clearance.

• Lateral clearance.

• Drainage.

• Toll collection.

• Interoperability. 

• Incident management.

• Design flexibility for future needs.

The careful consideration of the parameters shown above are important factors when planning a 

facility and should be considered in project’s development.

After identifying and assessing the design parameters and additional shoulder use considerations 

for a facility, the MPO and stakeholder groups need to assess the specific operating strategy(ies) for 

a facility. The factors to consider in this assessment include but are not limited to the pricing 

approach, time period variations and their impact on hours of operation, enforcement issues, 

incident management, evaluation and monitoring, marketing, and operations during construction. 

After careful assessment of all of these issues, the agencies can identify the most appropriate 

strategy or combination of strategies for a facility.

Chapter Summary

This document summarizes the implementation of safety shoulders as travel lanes as a method to 

increase the performance of the existing highway’s capacity. Its purpose is to provide a succinct 

overview of efforts to use left or right shoulder lanes as temporary or interim travel lanes. 

This chapter presents an introduction to the report, outlines the basic steps of the general planning 

process and where the critical consideration of shoulder use operational strategies fits into that 

process, and discusses design considerations. The reader should also have an appreciation of the 

shoulder use planning considerations that should be specifically addressed at the regional, corridor, 

or facility level in the process. Additionally, this chapter discusses the project development process 

as impacted by the consideration of shoulder use operational strategies. It presents the general 

steps in this process and offers insight into how an agency might incorporate shoulder use 
14

operational strategies to best meet the needs of the community at the corridor and facility levels. 

The reader should understand the importance of public and agency input, project identification and 

shoulder use assessment and project design.
Chapter 2: Context and Findings

Congestion in urban areas in the United States is increasing. It occurs on more roads during longer 

parts of the day, delaying more travelers every year. (6) The “rush hour” grows longer and costs 

Americans dearly in the form of delay, increased fuel consumption, lost productivity, and related 

crashes. Congestion interferes with daily life, and any method to alleviate it, such as managed lanes 

projects, can help reduce its impact on productivity. Another reality of improving the 

transportation infrastructure today is that agencies must function within environmental 

constraints. Agencies must consider the environment in the planning of transportation projects, 

minimize the negative impacts of construction, and work to reduce transportation-related pollution 

in the process. They must demonstrate environmental stewardship and improve the 

environmental quality of their transportation decision making. (7)

Congestion Management and Mitigation

Congestion management is a primary operational strategy that U.S. agencies use to operate their 

facilities. As illustrated in Figure 3, a variety of factors, both recurring and non-recurring in nature, 

cause congestion for American travelers. Thus, FHWA has designated congestion mitigation as one 

of its top priorities and is targeting resources on developing and sustaining regional partnerships to 

address all aspects of congestion. (8)

Figure 3. Graph. Causes of Congestion in the United States. (8)

Various operational and management strategies and methods exist for mitigating congestion and its 

impact on roadway users. For example, to combat recurring congestion in the highway 

environment, which accounts for approximately 45 percent of all congestion in the United States, 

agencies undertake freeway management and traffic operations through policies, strategies, and 

actions to enhance mobility on highway and freeway facilities. (8) These strategies include but are 
16

not limited to roadway improvements such as widening and bottleneck removal, operational 

improvements, ramp management and control, managed lanes, and ATM. Mitigation techniques for 

non-recurring congestion include incident management, work zone management, road weather 

management, and planned special events management. (8) All of these strategies center around the 

theme of increasing the efficient use of existing facilities. The following sections highlight two 

major categories of operational strategies that can be considered for deployment in shoulder use 

situations where capacity increases are not possible: managed lanes and ATM.

Managed Lanes 

The term “managed lanes” refers to an array of lane management strategies. These lanes are 

managed through the application of pricing, vehicle eligibility, or access control to expedite the flow 

in that lane. Figure 4 illustrates the potential lane management strategies that fall into this broad 

definition of managed lanes. On the left of the diagram are the applications of a single managed 

lanes operational strategy—pricing, vehicle eligibility, or access control. In the middle of the 

diagram are the more complicated managed lanes facilities that combine more than one of the 

strategies. The multifaceted facilities on the far right of the diagram are those that incorporate or 

combine multiple lane management strategies.

Figure 4. Graph. Lane Management Operational Strategies. (9)

According to FHWA, the distinction between managed lanes and other traditional forms of freeway 

lane management is the operating philosophy of “active management,” where the operating agency 

proactively manages demand and available capacity on the facility by applying new strategies or 

modifying existing strategies to meet pre-defined performance thresholds. (10) It is important to 
17

note that this definition does not preclude active management on other lanes in the roadway 

network.

Active Traffic Management

A 2006 FHWA-sponsored International Scan Tour of Europe (FHWA Scan Tour) examined the 

congestion management programs, policies, and experiences of other countries that are either in 

the planning stages, have been implemented, or are operating on freeway facilities. This scan 

sought information on how agencies approach highway congestion and how they are planning for 

and designing managed lanes at the system, corridor, and project or facility level. The FHWA Scan 

Tour revealed a complete package of strategies that make up the broader concept of active traffic 

management. This approach to congestion management is a more holistic approach and is 

considered the next step in congestion management of freeway corridors.

The FHWA Scan Tour defined ATM as the ability to dynamically manage recurrent and nonrecurrent congestion based on prevailing traffic conditions. (1) Similarly, the Transportation 

Research Board Joint Subcommittee on ATM defines it as the ability to dynamically manage traffic 

flow based on prevailing traffic conditions. (11) Focusing on trip reliability, the goal is to maximize 

the effectiveness and efficiency of the facility under both recurring and non-recurring congestion as 

well as during capacity reductions involving incidents or road work. Through the flexible use of the 

roadway, ATM aims to increase system performance as well as traveler throughput and safety 

through the use of strategies that actively regulate the flow of traffic on a facility. (11) ATM 

strategies can be automated, combined, and integrated to fully optimize the existing infrastructure 

and provide measurable benefits to the transportation network and the motoring public. Typical 

ATM strategies within the freeway context include bus operation on roadway shoulders, temporary 

shoulder use on freeways by general traffic or high occupancy vehicle s (HOV), speed 

harmonization, queue warning, dynamic rerouting, ramp metering, and interchange junction 

control. This report focuses on the first two of these strategies.

Shoulder Use—The European Experience

In Europe, part-time shoulder use is a congestion management strategy typically deployed in 

conjunction with complementary traffic management strategies – such as variable speed limits 

(speed harmonization) and/or ramp metering – to address capacity bottlenecks on the freeway 

network. European implementers include The Netherlands, Germany, and Great Britain. The 

strategy provides additional vehicle-moving capacity during times of congestion and reduced travel 

speeds. The use of the exterior shoulder during peak travel periods has been used in Germany 

since the 1990s as illustrated in Figure 5. (12) When travel speeds are reduced, dynamic signs over 

or next to the shoulder indicate that travel on the shoulder is permitted. 

A complete series of traffic signs indicate operations related to temporary shoulder use, including 

one with a supplemental speed limit indication (used when overhead gantries are not present). 

These signs and the overhead lane messages are blank when travel on the shoulder is not 

permitted. Temporary shoulder use is permitted only when speed harmonization is active and 

speed limits are reduced, thus providing an operating environment only when speeds are managed 

below posted levels. 
18

Figure 5. Photo. Temporary Shoulder Use—Germany (13). 

Generally, implementation of temporary shoulder use is at the discretion of the traffic management 

center operator, although traffic volumes help determine the need for the strategy. A typical 

installation in Europe incorporates a number of unique roadway features, which can include: 

• Lightweight gantries.

• Lane control signals.

• Dynamic speed limit signals.

• Dynamic message signs.

• Automated enforcement technology.

• Closed-circuit television cameras.

• Enhanced lighting.

• Roadway sensors.

• Emergency roadside telephones.

• Advanced incident detection.

• Intensified incident management.

• Emergency refuge areas or pull-outs beyond the shoulder. (1)

Operation of the system is handled by the regional control center, with operators on hand to 

monitor the system and initiate the modified operations as necessary. Specifically, operators use 

closed-circuit television cameras (CCTVs) mounted on lightweight sign gantries or separately to 

check for incidents and stalled vehicles in the shoulder before activating the system. 
19

In Great Britain, the first deployment of temporary shoulder use was part of a comprehensive 

traffic management system that also involved speed harmonization. Figure 6 shows the installation 

of the temporary shoulder use including a critical component, which is the installation of 

emergency refuge areas at 500-meter (m) intervals along the shoulder, each equipped with an 

emergency call box. 

Figure 6. Photo. Shoulder Use with Emergency Refuge Area—Great Britain. (1)

Plus Lane

The Netherlands, in addition to allowing temporary use of the right shoulder, also deploys 

temporary use of the left shoulder under congested conditions, as shown in Figure 7. The left lane, 

or plus lane, is opened for travel use when traffic volumes reach levels that indicate congestion is 

growing. As in Germany, temporary use of the left lane is allowed only when speed harmonization 

is in effect. Additional facilities implemented to mitigate any adverse safety consequences of 

temporary shoulder use include overhead lane signs, emergency refuge areas with automatic 

vehicle detection, speed reduction, variable route signs at junctions, advanced incident detection, 

CCTV surveillance, incident management, and public lighting. (14)
20

Figure 7. Photo. Plus Lane—The Netherlands. (1)

Junction Control

A variation of temporary shoulder use deployed in Germany is junction control, a combination of 

ramp metering and lane control at on-ramps. (15) Typically, the concept is applied at entrance 

ramps or merge points where the number of downstream lanes is fewer than upstream lanes. A 

graphic illustrating the concept is shown in

Figure 8. 

Figure 8. Graphic. Junction Control Schematic in Germany. (16)
21

In Europe, these strategies for managing recurrent congestion work to improve traffic flow and 

safety. The following is a summary of the three countries that are the main users of this strategy in 

Europe. 

The Netherlands

The Netherlands implemented temporary right shoulder use—also known as hard shoulder 

running or the rush hour lane—in 2003 as part of a larger program to improve use of the existing 

infrastructure. Operated by the National Traffic Control Center (NTCC) and regional control centers 

since 1981, temporary shoulder use is utilized on more than 1,000 km (620 mi) across The 

Netherlands. Typically, a gantry with lane control signals indicates when the shoulder is available 

for use. Where a shoulder lane passes through a junction and at the end of a hard shoulder running 

section, guidance information will change according to lane use. (14) In addition to allowing 

temporary use of the right shoulder, the Dutch also deploy the use of traveling on a dynamic lane on 

the median side of the roadway. This treatment—also known as the plus lane—is a narrowed extra 

lane provided by reconstructing the existing roadway while keeping the hard shoulder and is 

opened for travel use when traffic volumes reach levels that indicate congestion is growing. 

Deployment is automated based on field data and is initiated automatically based on an assessment 

algorithm, requiring no intervention by an operator. It only operates during time periods of 

congestion or when incidents occur along instrumented roadways.

Germany

Since 1996, Germany has deployed temporary shoulder use—also known as hard shoulder use—to 

provide additional capacity during times of congestion and reduced travel speeds. Operated by the 

Federal Ministry of Transport and regional traffic management center on more than 200 km of 

roadways across the country, temporary shoulder use is only deployed in conjunction with speed 

harmonization (also known as line control) when maximum allowable speeds are 100 km/hr (62 

mph) and if dynamic message signs are used for lane control. The deployment of the variable speed 

limits is automated based on field data and is initiated automatically based on an assessment 

algorithm, requiring no intervention by an operator.

Great Britain

Temporary shoulder use in Great Britain is deployed as part of an overall operational ATM scheme. 

Operated by the Highways Agency since 2006, temporary shoulder use is only deployed in 

conjunction with variable speed limits and when speeds are reduced (initially to 50 mph). 

Deployment of variable speed limits is automated based on field data and is initiated automatically 

based on an assessment algorithm, requiring no intervention by an operator. It only operates 

during time periods of congestion or when incidents occur along instrumented roadways, and 

between junctions, requiring users to exit at each junction and reenter the roadway beyond. 

Shoulder Lanes—The American Experience

In the United States, the primary use of shoulders has been as a safety refuge area. The limited 

shoulder use as a travel lane has been primarily reserved for special users of the roadway system, 

most often transit vehicles. Some shoulder use dates back to the 1970s, and many installations 
22

have been in operation for more than 10 years to address congestion on urban corridors. (17) 

Agencies have seen bus use of shoulders as a low-cost and quick strategy to improve bus operations 

and reliability without having to acquire additional right-of-way and invest additional large sums of 

money into the infrastructure. The length of these deployments varies depending on location, 

ranging from a more than 290-mi comprehensive network in the Minneapolis-St. Paul metropolitan 

area to deployments less than 1 mi in length used to serve as a queue jump for transit in Delaware. 

The operational strategies often depend on the congestion on the general purpose lanes and often 

require speed restrictions of the transit vehicles using the shoulders. (17) Overall, experience using 

shoulders for interim use has been positive in the United States, and more agencies are considering 

the strategy to address growing congestion on their urban freeway networks. In fact, several States 

have deployed temporary shoulder use for all vehicles on congested corridors with success. 

Another application that is much more difficult to research and document is the number of 

locations where an existing shoulder has been narrowed or taken away to allow for widening with 

an extra permanent travel lane. This method is more commonly used in roadway work zones to 

maintain the existing number of travel lanes during construction. However, it has been applied in 

some permanent forms as well. The following sections briefly describe the shoulder use treatments 

deployed in the United States and provide summary details about the deployments of those 

treatments in specific States.

Bus on Shoulders

Bus on shoulders (BOS) programs, generally considered special-use applications of dedicated 

shoulder lanes, are most often implemented as a means of increasing the reliability of transit 

service in congested corridors in order to encourage increased use by the public. The BOS 

programs are operational on over 290 mi of freeways and arterials in the Minneapolis metropolitan 

area. Shown in Figure 9, this operational strategy is generally a low-cost and quickly implemented 

solution that does not require costly expansion of highway right-of-way. It may be implemented on 

both highway and arterial corridors, but arterial BOS applications must often rely on additional 

operational treatments such as signal prioritization in order to maintain a time advantage over 

automobile travel. In addition to Minneapolis, BOS programs are operational in the States of 

Virginia, Maryland, Washington, New Jersey, Georgia, Delaware, Florida, and California; in Canada 

(Vancouver, Toronto, and Ottawa); and in Ireland and New Zealand. (17)

Besides stand-alone BOS operations, BOS may also be implemented in conjunction with a separated 

managed lane facility. Bus lines running a station-stopping operation along a median HOV or high 

occupancy/toll (HOT) lane may benefit greatly from the implementation of a BOS program. Such 

routes often make frequent stops at intervals of less than a mile between successive stops, which 

can pose significant problems with regards to weaving into and out of the HOV or HOT lane facility 

they access. This weaving can cause backups and disruptions on both the interior managed lane 

facility as well as the adjacent general purpose lanes. A BOS program ensures that buses can 

achieve significant travel time savings without the need to enter the interior managed lane facility 

and weave through general purpose traffic to enter or exit an interior managed lane. The following 

sections summarize the deployments of BOS in operation across the United States.
23

Figure 9. Photo. Bus on Shoulders—Mn/DOT (Photo courtesy of Mn/DOT).

California

In San Diego along I-805/SR 52, transit vehicles may use the freeway shoulder during congested 

periods. Initiated in 2005, this application was intended to increase transit speeds and to improve 

schedule reliability. Operating agencies are the California Department of Transportation 

(CALTRANS) and the San Diego Association of Governments. Transit vehicles may use the shoulder 

when general purpose lane traffic slows to 30 mph or lower. They may travel no more than 10 mph 

faster than traffic in general traffic lanes. The cross-section of the shoulder is at least 10-ft wide 

throughout the deployment area. Pavement markings to indicate the operational strategy include 

text indicating “Transit Lane Authorized Buses Only.” (17)

Delaware

Along US 202 in Wilmington, Delaware, buses are allowed to use an arterial shoulder. Operational 

for many years, this treatment is intended to provide a southbound queue jump along a 1,500-ftlong section of the facility, which includes an intermediate signal. The application provides priority 

for transit vehicles bound for I-95. Operational 24/7, the treatment is denoted with the diamond 

symbol on the pavement and lane control signals over the shoulder. (17) 

Florida

The Florida Department of Transportation, Miami Dade Transit, and the Miami Dade Expressway 

Authority operate several shoulder use applications in the Miami region. Along the Florida 
24

Turnpike, SR 826, and SR 836, buses are allowed to use the shoulder when the freeway is 

congested. Implemented in 2005, the program stipulates that buses may travel no faster than 

35 mph on the shoulder when open to transit. The typical cross-section is a minimum 10-ft width 

with a 12-ft width in high volume areas and cross slopes of 2 percent to 6 percent. Pavement 

markings indicate "Watch for Buses on Shoulder."(17)

Georgia

Alpharetta, Georgia (suburban Atlanta), is another location where shoulder use is available to 

transit. On GA 400, buses are allowed to use the freeway shoulder in an effort to provide access 

between a Metropolitan Atlanta Rapid Transit Authority rail station at North Springs and a parkand-ride lot at Mansell Road. In operation since 2005, the 12-mi facility allows transit vehicles to 

save between 5 and 25 minutes during heavily congested periods. The Georgia Regional 

Transportation Authority and Georgia Department of Transportation operate the facility, which is 

functional whenever traffic slows to 35 mph or slower. Buses can travel no more than 15 mph 

faster than general purpose lane traffic and are required to reenter general traffic lanes before 

interchanges. The installation cost 2.8 million dollars in order to widen the shoulder by 2 ft and to 

provide reinforcement of the shoulder pavement. (17)

Maryland

Two shoulder use applications are in operation in Maryland. The first, along US 29 in Burtonsville, 

is an arterial shoulder application in both the southbound and northbound directions of the 

corridor. The 4-mi arterial highway segment provides shoulder use queue jumps at several 

signalized junctions for transit users. Operational for years, the treatment operates Monday–Friday 

from 6:00 a.m. until 9:00 a.m. in the southbound direction and from 3:00 p.m. until 8:00 p.m. in the 

northbound direction. The second treatment, in Bethesda, provides buses with a shoulder queue 

jump in the northbound direction of I-495 at the I-270 interchange. This queue jump is about 3 mi 

in length and has been operational for years. The intent of the treatment is to allow transit vehicles 

to bypass congestion at the I-270 interchange. Hours of operation are Monday–Friday, 6:00 a.m.–

9:00 a.m. and 3:00 p.m.–7:00 p.m. The maximum allowed speed on the shoulder is 55 mph. (17)

Minnesota

The Minneapolis-St. Paul region has a comprehensive network consisting of over 290 mi of BOS 

operations on freeways and arterials, on sections with ramp meters, and in rural and urban areas. 

The BOS deployments are along segments as small as 0.3 mi to up to 9 mi in length. Initially 

deployed in 1992 and still being expanded, these deployments are intended to encourage transit 

use and to fully utilize the capacity of the metropolitan highway system. The operational partners 

of these facilities include the Minnesota Department of Transportation (Mn/DOT), Metro Transit 

and other transit agencies in the region, charter bus companies, Minnesota State Patrol, and local 

police departments. The operational strategy is considered interim, and some deployments have 

been removed since their inception. When operational, buses must yield to any vehicle entering, 

merging, or exiting through the shoulder. Buses must reenter the main lanes when the shoulder is 

obstructed. Typically, buses may use the shoulder any time that traffic in the adjacent mainlines is 

moving at less than 35 mph. Buses may travel no more than 15 mph faster than mainline traffic 
25

with a 35 mph maximum allowed speed on the shoulder. The typical cross-section is 10-ft 

minimum, 11.5-ft minimum at bridges, and 12-ft minimum on new construction. Typically, buses 

travel through the entrance and exit ramps; where queues are long at ramps with metering, buses 

typically merge with traffic on the ramp and return to the shoulder after the ramp. (18) 

New Jersey

In Mountainside, New Jersey, along Route 22, buses are allowed to use the shoulder of the arterial 

in the eastbound direction during congested periods. Operational for years, this shoulder use 

treatment was intended to allow transit vehicles to save travel time along the corridor toward 

Perth Amboy for about 1 mi. The facility is operated by the New Jersey Department of 

Transportation, and pavement markings indicate "Buses May Use Shoulder." (17)

Virginia

The Dulles Access Highway (Route 267) in Falls Church, Virginia, provides buses with an eastbound 

queue jump along a 1.3-mi segment. Operational for years, the treatment helps ease congestion for 

buses during the evening commute and facilitates bus access to the West Falls Church Metrorail 

station. Operated by the Virginia State Police, the Metropolitan Washington Airports Authority, and 

the Virginia Department of Transportation (VDOT), the shoulder treatment is available Monday–

Friday from 4:00 p.m. until 8:00 p.m. The maximum allowed speed for buses on the shoulder is 

25 mph. (17)

Washington

Along SR 520 in the Seattle, Washington, region, buses and carpools of at least three people may use 

the freeway shoulder in the westbound direction from I-405 to the Evergreen Bridge over Lake 

Washington. Operational since the 1970s, this 2.7-mi application operates 24 hours a day, 7 days a 

week. Buses can travel at the same speed as other general purpose lanes, but must merge with 

regular traffic at interchanges. The typical cross-section of the shoulder is 13-14 ft. (17)

Dedicated Shoulder Lanes

Since the 1950 publication of the Highway Capacity Manual and 1957 AASHTO Red Book, 12-ft 

shoulders have been the interstate design standard for urban freeways. (19) Furthermore, a 

minimum of 4.5-ft lateral clearance is required, with 6–8 ft recommended in the vicinity of pier 

structures. However, by the 1980s, in response to rising levels of congestion and a lack of right-ofway for contemporary expansion of capacity, many States adopted the use of dedicated shoulder 

lanes, sometimes in conjunction with or instead of narrowed lane widths. (20) By the 1990s, only 

four States had chosen to extensively use shoulders and/or narrow lanes on freeways: California 

(Los Angeles and Bay Area), Texas (Houston), Virginia (Fairfax County), and Washington (Seattle). 

Figure 10 shows a converted shoulder lane in California. 
26

Figure 10. Photo. Converted Shoulders on I-5—California (Photo Courtesy of CALTRANS).

In dedicated shoulder-lane operations, either general purpose or HOV-specific capacity has been 

added through the permanent conversion of shoulders. Most HOV applications use the interior lane 

for HOV operations, while the exterior shoulder is used for general purpose traffic so as to maintain 

the same number of general purpose lanes that existed prior to implementation. A typical HOV 

application would convert a three-lane freeway with 12-ft lanes, 10-ft exterior shoulder, and 8-ft 

interior shoulder to 11-ft general purpose lanes, 14-ft (including buffer striping) HOV lane, 5-ft 

exterior shoulder, and 2-ft interior shoulder. (21) 

In addition to HOV and general purpose capacity, additional existing uses of shoulders include 

auxiliary lanes, either between interchanges or in merge zones (particularly those that impede 

upstream traffic on the mainline); lane balancing requirements through bottlenecks; and creation 

of uniform lane widths. (19)

In most of the above conditions, the shoulders have been converted to general purpose capacity, at 

least for a short distance. However, in a few applications, the implementing agency has attempted 

to recover use of the shoulder for refuge purposes during some portions of the day. On 

Massachusetts State Route 3 and I-93 and I-95 in the Boston area, all vehicles are permitted on 

shoulders in the peak periods only. Similarly, in Virginia on I-66 (as shown in Figure 11), the 

shoulder carries general purpose traffic from 5:30 a.m. –11:00 a.m. (eastbound) and 2:00 p.m.–8:00 

p.m. (westbound); however, during this time, the interior general purpose lane is open to HOV 

traffic only. I-66 uses extensive traffic signals and signage in order to communicate the active times 
27

of service. In the Seattle area, the right shoulder on the US 2 trestle near Everett is opened to all 

traffic in the eastbound direction during the afternoon peak period. A similar operation is provided 

on H1 in Honolulu in the morning peak on the right shoulder. The following sections provide a 

summary of those States where temporary shoulder use is available for all vehicles during 

congested periods.

Figure 11. Photo. I-66 HOV/Shoulder Lane Adaptation—Virginia (Photo Courtesy of VDOT).

Florida 

As part of an Urban Partnership Agreement project, the Florida Department of Transportation 

(FDOT), the Miami-Dade MPO, the Broward MPO, Miami-Dade Transit, Broward County Transit, the 

Miami-Dade Expressway Authority, and the Florida Turnpike Enterprise have incorporated a 

shoulder into the I-95 Express lanes in Miami. (22) The objective of the project is to provide freeflowing conditions on the managed-lane network and to provide a network of managed lanes 

throughout the congested region. Between I-395 and I-595, FDOT converted the existing singlelane HOV lane to a two-lane HOT facility by reducing multiple general purpose and HOT lane widths 

to 11 ft and narrowing the shoulder. The new lanes allow registered vanpools, registered carpools 

of three people, registered hybrid vehicles, motorcycles, and buses to travel at no charge. All other 

vehicles with the exception of trucks with three or more axles may pay a toll to use the lanes. With 

initial sections opening in 2008, the facility uses variable pricing based on demand, and maximum 

allowed speeds are 55 mph. Operational regulations and toll rates are displayed on overhead 

electronic signs. The overall cost of the project is 43.4 million dollars. Florida's Turnpike 

Enterprise enforces toll violations using license plate photographs. The Florida Highway Patrol
28

enforces occupancy requirements using visual inspection. Incident management is handled by the 

Road Rangers motorist assistance patrol and the Florida Highway Patrol. Outreach efforts for the 

project include project Web sites, public meetings, media campaigns, and the production of videos. 

Hawaii

In Honolulu, Hawaii, the Hawaii Department of Transportation deploys temporary shoulder use on 

H1 in the morning peak. The intent is to provide congestion relief and added capacity during the 

morning rush hour in the eastbound direction.

Massachusetts

Various facilities in the Boston area utilize temporary shoulder use during peak travel periods. (23) 

On I-93, SR 3, and I-95, all vehicles except heavy trucks may use the freeway shoulder during either 

the morning and/or evening peak depending on the facility. The objective of these treatments is to 

increase capacity. When the treatment was initiated, congestion on these facilities was to the point 

where traffic during the peak period was at a standstill and drivers were already using the 

shoulders. The Massachusetts Department of Transportation (MassDOT), Massachusetts State 

Police, and Commerce Insurance Courtesy Patrol all assist with the operation of the facility. With 

each deployment, MassDOT sought approval from FHWA to seek implementation as a temporary 

measure until funding and approval is obtained for widening. However, each project when 

constructed was treated as a traditional widening with drainage being moved to the new edge of 

the pavement and guardrails and fixed object shielding being moved accordingly as well. The 

typical design is a 10-ft minimum width and a 12-ft desirable width. Rumble strips were removed

and scored concrete and block pavers removed as well. Emergency pull-outs are located 

approximately every 1⁄2 mi along the deployment sections. 

Minnesota

In Minneapolis along I-94, the freeway shoulder was opened to all traffic in 2007 in response to the 

bridge collapse on I-35 W. (24) All vehicles were allowed to use the shoulder, which was originally 

only available to transit vehicles during peak periods. The objective of the treatment was to reduce 

congestion levels to pre-bridge collapse conditions by providing additional capacity through 

utilization of existing shoulders. Operational at all times, the shoulder provides an 11-ft travel lane

with no additional shoulder on the right side. Traditional lane skip stripe and right shoulder 

markings are installed, and the existing BOS signs were removed. Incident response along the 

facility is handled by the Freeway Incident Response Safety Team (FIRST) led by Mn/DOT. Patrols 

were increased in the area once all vehicles were allowed to use the shoulders. 

Virginia

In the suburban Washington, D.C., area, all vehicles are allowed to use the right shoulder on I-66 

during peak periods. (25) Originally opened in 1992, the VDOT allows vehicles to use the eastbound 

shoulder from 5:30 a.m. until 11:00 a.m. and the westbound shoulder from 2:00 p.m. until 8:00 p.m. 

The treatment was initially installed as a stop-gap measure to add capacity because of the opening 

of the HOV lane, where the left lane was taken. However, it has become a long-term strategy 

because of funding shortfalls. Maximum allowed speeds are 55 mph, and the shoulder provides a 
29

12-ft travel lane. An overhead lane control system is operational to indicate to motorists that the 

shoulder is open. Post-mounted signs also provide notification and termination of restricted use

and indicate the presence of emergency pull-off areas. The VDOT hires a contractor for general 

maintenance of the facility, while VDOT maintains the Intelligent Transportation System (ITS) 

installation. Incident clearance time is within 90 minutes 90 percent of the time, as typical for the 

region. 

Washington

Along US 2 in Seattle, the Washington State Department of Transportation (WSDOT) opened the 

freeway shoulder to all traffic in the eastbound direction of the trestle. (26) The objective of the 

treatment was to improve travel times on the trestle, to reduce impacts of bottlenecks, and to 

relieve congestion at a critical interchange. The restriping along the 1.55-mi segment allows three 

different movements to remain in their own lanes when shoulder use is allowed. It also minimizes 

weaving so that each destination from the trestle (SR 204, 20th St SE, and US2 eastbound) can be 

reached from a separate lane when shoulder use is allowed. The WSDOT considers the application 

permanent for the near future as it should be able to accommodate traffic growth over the next few 

years. Hours of operation are Monday–Friday, 3:00 p.m. to 7:00 p.m. Maximum allowed speeds are 

60 mph. The trestle was restriped with a 2-ft left shoulder, two 11-ft lanes, and one 14-ft right 

shoulder. 

Priced Dynamic Shoulder Lanes

A unique combination of strategies is operational on I-35W in Minneapolis where a segment has the 

left shoulder open during the peak periods. Known as priced dynamic shoulder lanes (PDSL), 

transit and carpools use the shoulder for free and MnPASS customers can use the shoulder for a fee. 

As shown in Figure 12, Figure 13, and Figure 14, the left shoulder is open to traffic, with overhead 

sign gantries indicating its operational status. When the general purpose lanes become congested, 

the shoulder is opened and the speed limit on the general purpose lanes is reduced. 

Figure 12. Graphic. Open Priced Dynamic Shoulder Lane—Minneapolis, Minnesota. (27)
30

Figure 13. Graphic. Closing Priced Dynamic Shoulder Lane—Minneapolis, Minnesota. (27)

Figure 14. Graphic. Closed Priced Dynamic Shoulder Lane—Minneapolis, Minnesota. (27)

Minnesota

In Minneapolis, Mn/DOT converted a segment of the left shoulder on I-35W from BOS operations to 

a priced dynamic shoulder lane open to all vehicles. Opened in 2009 as part of Mn/DOT’s Urban 

Partnership Agreement project, the section of I-35 between 42nd Street and downtown 

Minneapolis is open to buses, carpoolers, and MnPASS users during certain times when traffic is 

congested. (27) The objective of the project is to improve traffic flow using transit and tolling. The 

shoulder treatment was also deployed with variable speed limits on the general purpose lanes. 

Maximum allowed speeds are free-flow freeway speeds on the facility. The shoulder width varies 

from 17 ft to 19 ft between the barrier and the edgeline striping. Overhead gantries are spaced 

every 1⁄2 mi and include static signs and dynamic message sign (DMS) inserts indicating price and 

lane control signals. The cost of the deployment was 13 million dollars and included new pavement 
31

surface on all lanes in the area. The Minnesota State Patrol enforces the facility through visual 

inspection. The Mn/DOT is responsible for maintenance, and incident management response is 

primarily handled by the Minnesota State Patrol. Emergency pull-outs were installed along the 

right shoulder to facilitate emergency use. In terms of heavy vehicles, only two-axle trucks 

weighing less than 26,000 lbs can use the MnPASS Express Lanes. 

Hurricane Evacuation Routes

Florida and Texas have incorporated the use of certain freeway shoulder lanes into Hurricane 

Evacuation Routes. These lanes are included in the Evacuation Route planning documents for full 

scale evacuations.

Complementary ATM Strategies

European applications of the use of shoulder lanes are typically accompanied by one or more ATM 

operational strategies for a more comprehensive control of the capacity. When these strategies are 

implemented in concert with temporary shoulder lanes, they fully optimize the existing 

infrastructure and provide measurable benefits to the transportation network and the motoring 

public. The more frequently used complementary strategies include speed harmonization and 

junction control. The following sections discuss these strategies to provide a framework for their 

impact on shoulder use for travel lanes.

Speed Harmonization

Speed harmonization helps manage traffic by posting speed limits on a roadway or over each lane 

on an advisory or regulatory basis in real time, sometimes referred to as variable speed limits in the 

U.S. This approach has been in use in Germany since the 1970s and is oriented toward improving 

traffic flow based on prevailing conditions. Similar installations are in operation in The 

Netherlands and Great Britain on various roadway sections with high traffic volumes. A typical 

installation of speed harmonization monitors traffic volumes and weather conditions along the 

roadway. If sudden disturbances occur in the traffic flow—such as with an incident or building 

congestion—the system modifies the speed limits upstream accordingly, providing users with the 

quickest possible warning that roadway conditions are changing. (28) 

Figure 15 shows a typical installation of speed harmonization in The Netherlands. The deployment 

of the speed harmonization is automatic and begins immediately upstream of the congestion point; 

it does not require remote operator intervention. The system incrementally decreases speeds 

upstream in a cascading manner often in increments of 10 to 20 km/h to smooth the deceleration of 

the traffic and help ensure more uniform flow to offset what would otherwise be sudden queues 

emanating from the incident. When deployed with temporary shoulder use, this strategy works to 

minimize the speed differential between vehicles in the general purpose lanes and those on the 

shoulders. Such a combined operation helps to increase the uniformity of traffic flows and reduce

the possibility of incidents due to erratic maneuvers and unpredictable driver behavior.
32

Figure 15. Photo. Speed Harmonization—The Netherlands.

Junction Control

A variation of temporary shoulder use—known as junction control in Germany—involves dynamic 

lane assignment. Typically, the concept is applied at entrance ramps or merge points where the 

number of downstream lanes is fewer than upstream lanes. (15) The typical U.S. application to this 

geometric condition would be a lane drop for one of the outside lanes or a forced merge of two 

lanes, both of which are static treatments. (29) The German dynamic solution is to install lane 

control signals over both upstream approaches before the merge (as shown previously in Figure 8), 

and provide downstream lane priority to the higher volume and dynamically post a lane drop to the 

lesser volume roadway or approach. This is particularly effective when implemented with 

temporary shoulder use at on-ramp locations where bottlenecks frequently form. 

Chapter Summary

Many urban corridors in most large cities have been expanded to the extent feasible from 

subsequent widening projects, leaving few options to improving performance and efficiency other 

than ATM strategies. Limited resources require investments in strategies that generate greater 

efficiencies without requisite environmental or safety impacts. The current fiscal and physical 

environment lends itself to greater reliance on these strategies. Identifying potential active 

management projects and planning for them is a complicated process that involves numerous 

stakeholder groups. Addressing the interrelationships associated with these projects in the 

planning and development process is critical to their successful implementation and operation. 
33

The summary of shoulder use applications provides a stark contrast between European and U.S. 

applications. Part-time shoulder use in Europe is exclusively done as part of a broad application of 

active traffic management strategies. The domestic applications have tended to be more ad-hoc 

and have much less consistency from one application to the next. The one exception is the PDSL in 

Minnesota, which has an active traffic management design.

35

Chapter 3: Critical Issues

The primary concern related to shoulder use involves its impact on operations and safety. The 

purpose of this project was to assess the deployments of shoulder use in the United States and 

determine the impacts on, the experience with, and the addressing of the following safety issues:

• Conflicts at access ramps.

• Sight distance.

• Conflicts with motorists pulling onto the shoulder for emergency purposes.

• Loss of use of the shoulder for emergency refuge.

• Need for bus driver training.

• Speed differential between the general purpose lanes and the shoulder.

• Effect on general purpose lane users.

• Return merge distance adequacy.

• Debris hazards on shoulder.

• Reduced bridge clearance.

• Drainage.

• Operational efficiency.

• Crash experience.

By providing a summary of this information and data related to shoulder use experience, it is 

expected that the project can assist FHWA with developing guidance on the subject and identifying 

what, if any, research needs to be conducted to address unknowns related to the operational 

strategy and its potential long-term and widespread use in the United States.

Through the course of this effort, the project team conducted a thorough informational scan and 

literature search to identify the existing state of the practice and relevant traffic and safety 

information associated with safety shoulder usage. Furthermore, they conducted personal 

telephone interviews to seek additional direct input from various agencies that are known for their 

use of shoulders for interim or long-term congestion relief. The study regions interviewed were 

Minneapolis-St. Paul, Virginia, Massachusetts, and Washington. The following sections highlight the 

critical operations and safety issues related to shoulder use that arose from these activities. 

Individual case studies on several operational facilities are included in Chapter 4. The interview 

questions used by the project team are included in appendix A. 

Design

It is always desired to have a minimum 12-ft lane width for all freeway travel lanes. A reduction in 

this lane width reduces the overall capacity and may impact smooth operations. However, with 

regard to temporary shoulder use, narrower lane widths can be acceptable due to the limited use 

and operating conditions during their use. For example, the Mn/DOT uses a minimum 10-ft 

shoulder as an acceptable width on those facilities where BOS is operational. (18) Where the BOS 

travels across a bridge, 11.5 ft is a required minimum, with 12 ft being the minimum for new 

construction that may accommodate BOS. The narrow width does not adversely impact operations 
36

given the lower speeds of the transit vehicles (35 mph maximum) and controlled speed differential 

(buses can travel no more than 15 mph faster than the main lane traffic). Additionally, Mn/DOT 

restriped the shoulder on I-94 to 11 ft when converting the shoulder after the collapse of the I-35W 

bridge. (24) Additionally, the shoulder on I-35W where Mn/DOT has deployed priced dynamic 

shoulder lanes on a former BOS left shoulder ranges in width from 17 ft to 19 ft from the barrier to 

the edgeline stripe. 

The temporary shoulder use on I-66 in Virginia does have 12-ft lanes throughout the facility. (25) No 

special concerns or accommodations have been needed for over-width vehicles in some States. (18),

(24), (26) However, in Massachusetts, no heavy trucks are allowed on the shoulder, and only two-axle 

vehicles weighing less than 26,000 lbs can use the MnPASS PDSL on I-35W. In Virginia, there are 

some locations along I-66 where a small amount of pavement, ranging from 1 ft to 12 ft, remains 

outside of the shoulder to help with wider vehicles. While this width is not huge, it can be helpful in 

some circumstances. In Massachusetts, the minimum shoulder width required is 10 ft with a 

desired being 12 ft. (23) The WSDOT restriped the US 2 trestle to provide a 2-ft left shoulder, two 

11-ft lanes, and a 14-ft right shoulder where the shoulder use is permitted. (26) With the I-94 

installation in Minnesota, the shoulders were not widened prior to allowing all vehicles to use the 

shoulder. The agencies were confident that the shoulders could handle the additional traffic 

without compromising the pavement integrity. With the Mn/DOT BOS deployments, each 

installation is unique. Thus, if the agency determines the shoulder can handle the additional bus 

traffic, no pavement widening is undertaken. For other situations, Mn/DOT has developed cost 

estimates for BOS deployments if shoulder improvements are needed, recognizing that all facilities 

may not be able to handle the additional traffic. 

One of the potential challenges with using shoulders for travel lanes is the presence of fixed objects 

within the recovery area of the shoulder. With the Mn/DOT BOS applications, fixed object shielding 

is not installed since the shoulders are only used when speeds are low and congestion is present. In 

some cases, though, the agency has had to move guardrails to provide the 11.5-ft minimum 

pavement width. If an object is such that it cannot be moved, Mn/DOT requests a design exception 

for the case. Along the I-94 shoulder use installation, some fixed object shielding was installed 

because of ramp reconfigurations, and some retaining walls were installed to accommodate the 

widening where the shoulder was not adequate in width. In Virginia on I-66, some barriers were 

extended to address fixed object issues. Furthermore, some deceleration lanes were shortened and 

acceleration lanes extended for the same reason. In Massachusetts, each of the shoulder use 

deployments was treated like a traditional widening project where guardrails and fixed object 

shielding were moved to appropriate locations. 

Treatment at Interchanges

In the domestic applications of temporary shoulder use, the vehicles traveling in the shoulder lane 

traverse across the entrance and exit ramps as they would if they were in the main lanes. (18), (23), (24), 

(25) Of interest is the BOS operating rules in Minnesota. On those facilities with BOS, buses must 

yield to any vehicle entering, merging within, or exiting through the shoulder. (18) Also, if the ramp 

meter at an entrance ramp is creating significant queues, many transit drivers will merge into the 

general purpose lane to allow the ramp traffic to merge without conflict with the buses. This 
37

maneuver is not mandatory of drivers, but those with significant experience normally execute it to 

enhance freeway operations. Once they pass the ramp, they move over onto the shoulder and 

proceed. In Germany and The Netherlands, vehicles on the shoulder continue on the shoulder 

through an entrance or exit ramp. However, in England, drivers on the shoulder must exit the 

motorway at the interchange, travel through the intersection at the junction, and reenter the 

motorway to continue traveling on the shoulder. 

Drainage

In general, agencies have made improvements or changes to drainage inlets on those facilities with 

shoulder operations. In Minnesota, those catch basins on the facilities with BOS are reinforced as a 

precautionary measure. They are also raised to be flush with the pavement so that operations are 

not impeded. (18) Along I-94, no additional drainage inlets were installed prior to opening the 

shoulder to all users, as the conversion was a weekend operation that needed a quick turnaround. 

With the I-66 installation in Virginia, some design exceptions, which were most likely approved as 

cross-slopes along the facility, are different than what is typical for other like roadways. (25) Other 

drainage issues that have arisen as a result of cross-slope issues have been resolved with the 

installation of additional inlets. In Massachusetts, projects were treated as traditional widening 

projects, and drainage inlets were moved to the new edge of pavement.

Drainage capacity needs to be reviewed for a design year storm. While some stormwater storage 

might be acceptable on a safety shoulder, the same is not the case on a travel lane.

Emergency Refuge Areas

Perhaps the most critical concern regarding the use of shoulders as travel lanes is the inability for 

vehicles to use the shoulder in the event of an emergency. This condition can be minimized by 

installing emergency refuge areas (ERAs) periodically along the facility. Along the M42 in England, 

emergency refuge areas are located approximately every 500 m and include emergency roadside 

telephones. The telephones are accessible to wheelchair users, located behind safety fencing, and 

feature text messaging and eight different languages. (30) With regard to the design of these ERAs, 

the entrance taper is 25 m and the exit taper is 45 m. In Virginia on I-66, emergency pull-outs are 

located wherever space was available. The lowest spacing is less than 0.5 mi, with the greatest 

spacing being 2.5 mi between pull-out areas. Additionally, there are a number of locations 

designated as "informal" pull-outs where traffic can pull out of the shoulder lane into a safe area. 

These areas are located where space permits and are often narrower than a formal shoulder pulloff. However, they do provide some refuge area that is better than none at all. Entrance and exit 

tapers are typically 300 ft along the corridor. In Massachusetts, emergency pull-out areas are 

located approximately every 1⁄2 mi, and those installed along I-35W in Minneapolis are located off 

the right shoulder to handle emergency stops while the left shoulder is under use. (24)

Rumble Strips

The Mn/DOT is one agency that has dealt with rumble strips along the facilities with BOS. On those 

roadways with rumble strips on the shoulder, designers either move the rumble strips so that the 

buses straddle the strips, or install rumble stripes on the pavement marking. In both cases, the 

transit vehicles avoid driving on the affected pavement. (18) The MassDOT removed rumble strips 
38

where the shoulder operations were deployed and also removed scored concrete and block pavers 

that would affect driving performance on the shoulders. (23)

Safety Studies

The safety benefits from the U.S. applications have mostly been inconclusive. However, there are 

specific safety benefits noted in the European case studies. In fact, it is the safety benefits that have 

been the leading success stories of these applications. It should be noted that these shoulder use 

applications also have a major investment in active traffic management strategies. In addition, 

these systems require significant investment in ongoing maintenance, operations, and system 

control manpower.

Future U.S. studies should also address the freeway sections upstream of the shoulder use section 

to get the full appreciation of safety benefits. Many congestion related crashes happen well in 

advance of the actual bottleneck location as traffic queues as a result of the congestion.

ITS Components

The ITS components of the shoulder use deployments varied by location. (18), (23), (24), (25), (26) In 

Minnesota, components included those typical across the region, including cameras and loop 

detection. Virginia installed loops in the shoulder pavement and ensured that camera coverage was 

adequate in the corridor. The WSDOT did not install any additional components along the segment. 

Massachusetts has some sensors on I-93, along with cameras.

Traffic Control Devices

Most of the traffic control devices deployed with shoulder use are regulatory in nature. The VDOT 

uses an overhead regulatory sign—displayed in Figure 16—to indicate shoulder operations. The 

regulatory sign is combined with a lane control signal to indicate when drivers may use the 

shoulder. Other ground-mounted signs used on the installation include a regulatory sign with 

hours of operation (Figure 17), a regulatory sign noting the presence of an emergency pull-off 

(Figure 18), and regulatory signs indicating the beginning and ending of the shoulder operations 

(Figure 18).
39

Figure 16. Photo. I-66 Regulatory Sign with Lane Control Signals (Photo Courtesy of VDOT).

Figure 17. Photo. I-66 Hours of Use Regulatory Sign (Photo Courtesy of VDOT).
40

Figure 18. Photo. VDOT I-66 Regulatory Signs (Photo Courtesy of VDOT).

The Mn/DOT uses ground-mounted signs to indicate BOS operations. The two signs most 

frequently used are the regulatory sign stating that only buses are authorized to use the shoulder 

(Figure 19) and a warning sign for transit vehicles indicating they should merge with traffic (Figure 

20). Pavement markings for all operations are no different than normal shoulder edgeline 

markings. It is important to note that it is not advisable for an agency to install the special use lane 

diamond on the shoulder to indicate temporary shoulder use. (18) This marking is commonly 

associated with HOV operations, so drivers may assume that HOVs are allowed to use the shoulder 

at all times. This assumption is of particular concern in Minnesota where only buses are allowed to 

use the shoulders and only during peak periods of travel. 
41

Figure 19. Photo. Mn/DOT BOS Regulatory Sign (Photo Courtesy of Mn/DOT).

Figure 20. Graphic. Mn/DOT BOS Warning Sign (Image Courtesy of Mn/DOT).

The MassDOT uses a combination of regulatory and warning signs to indicate that the shoulder is 

open to all users during specified times. As noted in Figure 21, regulatory signs are used to indicate 

the hours of operation and shoulder use prohibition during non-operating hours. The sign in Figure 

22 is displayed to warn drivers to expect vehicles in the right breakdown lane during the shoulder 

use operating hours. Regulatory signs are also used to indicate the location of emergency pull-off 

areas.
42

Figure 21. Photo. Regulatory Shoulder Use Signs (Photo Courtesy of MassDOT). (23)

Figure 22. Photo. Warning Shoulder Use Sign (Photo Courtesy of MassDOT). (23)

The Mn/DOT uses overhead sign gantries with a combination of static guide and regulatory signs, 

lane control signals, and DMS panels to indicate the operational status of the PDSLs and the 

MnPASS fee for using the lanes. These signs are illustrated in Figure 12, Figure 13, and Figure 14. 

The WSDOT uses a regulatory sign, as shown in Figure 23, to provide information to the user 

indicating when the shoulder is open and when it is closed. (26) While none of the signs used by the 
43

various States are identical in nature, they all fall within the guidance provided by the Manual on 

Uniform Traffic Control Devices (MUTCD). (31) Moreover, the agencies are confident that motorist 

comprehension of these signs is high when combined with public outreach.

Figure 23. Drawing. Shoulder Use Regulatory Sign (Drawing Courtesy of WSDOT). (26)

Pavement Markings

There has been inconsistency in both the U.S. and Europe on the use of an outside edge line on the 

shoulders used as travel lanes. This is an area for further research and analysis.

Performance 

Performance evaluation of shoulder lanes principally derives from two domestic sources—National 

Cooperative Highway Research Program (NCHRP) Report 369 (32) and an independent evaluation of 

I-66 (33)—and one international source—the M42 Program Evaluation. (34) The findings from these 

sources are summarized here along with other information provided by Mn/DOT, MassDOT, and 

WSDOT related to their facilities.

Operations

The NCHRP 369 provided a comparative benchmark analysis methodology of eleven corridors in 

six States, using in-corridor comparisons of “unaltered” segments (full shoulders with 12-ft lanes) 

and “altered” segments (use of shoulders with or without narrow lanes). (32) The evaluation 
44

hypothesis postulated that the lack of shoulders and/or use of narrow lanes would result in 

different operating conditions.

When isolated by level of service (LOS) categorizations, travel speeds on segments with use of 

shoulders/narrow lanes were not significantly different from their interstate standards brethren in 

low-volume and high-volume applications. However, there was a minor difference in speeds in 

medium-volume applications: 

• Level of Service A/B: With volumes less than 1,600 vehicles per hour per lane (vphpl), 

speeds were identical between altered and unaltered facilities.

• Level of Service C/D: A slight decrease (less than 5 mph) in average travel speeds was 

found in altered facilities when volumes ranged between 1,600 vphpl and 2,000 vphpl. 

This was the only statistically significant difference.

• Level of Service E/F: Like LOS A/B, there was no difference in speeds between altered 

and unaltered facilities at volumes higher than 2,000 vphpl.

At LOS C or worse, there was no significant difference in the choice of lanes (shoulder vs. static 

lanes) by travelers. However, at LOS A or B, the use of shoulder lanes was significantly less 

prevalent, especially if the surface of the shoulder was different from the travel lanes. On part-time 

shoulder facilities (such as SR 3 and I-93 in Massachusetts and I-66 in Virginia), if traffic remains 

slow and the time is outside the operational shoulder-lane time period, drivers may ignore the 

shoulder-use restriction and use the lanes anyway. This complicates the ability of the operating 

agency to recapture the shoulder as a refuge area. In addition to the difference in average speeds, 

altered facilities exhibit a greater range of speeds in LOS C/D conditions (30–70 mph) than 

unaltered LOS C/D conditions (50–70 mph). 

Lateral clearance effects of altered facilities did have an impact on drivers, causing them to shy 

away from the barrier. The percent of traffic within a foot of the interior lane line (regardless of 

lane) was lower at altered sites than unaltered ones. As would be expected, inadvertent lane-line 

crossings per hour increased significantly with altered sites compared with unaltered ones. 

When Mn/DOT converted the BOS on I-94 to all vehicles in response to the collapse of the I-35W 

bridge, traffic congestion improved along the facility. In both directions, the length of queues and 

duration of congestion improved to near pre-collapse conditions, and travel times improved as 

well. (18) One negative impact of the elimination of the BOS was on transit performance on the 

facility. While previously transit vehicles enjoyed reliable travel times on the shoulders, once other 

vehicles were allowed to use the shoulders, that advantage disappeared. Metro Transit lost 

revenues of approximately 1.3 million dollars per year in fixed guideway funds from FTA as a result 

of the dedicated lane being eliminated. In terms of BOS on other facilities in the Minneapolis region, 

transit vehicles maintain a reliable travel advantage.

While only recently deployed, the shoulder operations on US 2 in the Seattle area have greatly 

improved conditions for the regional commute along that corridor. The primary performance 

measure WSDOT is using is travel time, and delay has fallen from 8-10 minutes to 1-2 minutes on 
45

the facility. (26) Travel times are much more reliable on the facility, and throughput has increased 

on a previously congested ramp. 

Safety

As early as the late 1970s, agencies experimented with using freeway shoulders to increase 

capacity. A 1978 study of restriping the US 59 main lanes in Houston, which encroached on the 

shoulder and increased capacity, yielded positive results in terms of operations and safety. (21) With 

the Houston implementation, operations were improved during peak travel periods, travel time and 

quality of operation improved, and accident frequencies and rates dropped in the year after the 

deployment. However, a similar study of inside shoulder removals in California did not yield any 

significant reduction in overall accident rates as a result of the shoulder removal. (20) Instead, the 

research indicated that the drop in accident rates was a result of a decrease in congestion due to the 

capacity increase.

Initial safety reviews in the 1980s of shoulder lane usage indicated that projects implemented for 

short distances to address specific problems often yielded a decline in accident rates. However, the 

NCHRP Report 369 introduced an alternate methodology to examine accident severity, time of day, 

type of accident, and characteristics to validate the initial findings. Corridors examined were I-395 

(Virginia), I-5 (Washington), I-5 (California), I-85 (Georgia), and I-10 (California). (32) Statistical 

analysis indicates that in aggregate across the study corridors, there was no significant difference 

between altered and unaltered segments. However, significant increases in accidents (up to 36 

percent more in some segments on I-5) occurred in one specific alteration: a combination of use-ofshoulders and narrow lanes for greater than 1 mi in length. Under these conditions, accident 

frequency increased significantly, as did sideswipe, nighttime, and truck accidents. (35)

On I-66 in Virginia, investigators found no significant impact of the combined managed-lane (HOV) 

and shoulder-lane (general purpose) operations on traffic crash frequency. The majority of crashes 

were rear-end collisions, which are typically a result of congested conditions. Authors 

hypothesized that advanced incident identification and clearance as well as enhanced dynamic 

messaging signs contributed to the lack of evidence that the system increased crashes. Since the 

implementation of BOS in Minnesota in 1993, only 21 collisions have occurred related to the 

operations, most of which were sideswipes or mirror hits on the bus. 

While it is too early to confidently assess safety improvements along US 2 in Washington, anecdotal 

evidence shows that collisions at the conflict point just upstream of the shoulder usage have been 

reduced. (26) However, it is difficult to measure the true isolated impact of the shoulder use since its 

deployment coincided with the deployment of ramp metering on I-5, which feeds into the US 2 

trestle. 

A critical concern with the deployment of shoulder use is the reduction of the clear zone distance. 

While an agency may be able to move some fixed objects, guardrails, and other barrier treatments, 

such accommodation is not always possible. Thus, when traffic is allowed to travel in the shoulder, 

the effective clear zone is reduced to distances below the minimum allowed. As a result, agencies 
46

frequently have to seek design exceptions from FHWA. The potential long-term implications of 

these exceptions are not known and bear consideration for any possible deployments.

Maintenance

The implementation of shoulder lanes has yielded higher costs and more difficult maintenance 

activities. Maintenance-related issues as identified by the NCHRP Report 369 include:

• Under altered conditions, highway appurtenances such as signage, barriers, drains, and 

lights were closer to traffic and were damaged more often and more severely than 

under unaltered conditions.

• In order to conduct regular maintenance, additional personnel and equipment are 

needed to close lanes and provide adequate work area protection.

• Most incidents, from minor to major, require some action by personnel that involves 

shoulders, which in turn requires shoulders to remain closed until the incident is 

cleared, items are removed, or other action is completed. Estimates by personnel 

indicate that clearance time for incidents doubles with shoulder lane use.

• As emergency vehicles use shoulders to access scenes of accidents, delays in arriving on 

the scene have consequent increases in periods of congestion, secondary accidents, and 

clearance time. 

Enforcement

Enforcement is not a problem on those Mn/DOT facilities with BOS. Most of the enforcement issues 

addressed by Minnesota State Patrol have more to do with ensuring that cars do not block the buses 

on the shoulder on purpose. ( (18)) Visual inspection and using radar to clock the speeds of buses are 

the methods of enforcement. Those buses that are traveling faster than 35 mph while on the 

shoulder are reported to the transit agencies, and the drivers receive a reprimand. Never have 

repeat complaints about speeding been received by Metro Transit or Mn/DOT because the drivers 

realize that their job depends on following the operational rules and requirements. 

Enforcement along I-66 is difficult for both Virginia State Police and county law enforcement 

personnel. The short distance and tight interchange spacing makes enforcement a challenge for 

officers wishing to cite a driver using the shoulder during the off-peak period. (25) However, the 

high off-peak violations do not present a safety problem because of the short distances between 

interchanges. 

Enforcement activities in Massachusetts and Washington are typically handled by State police 

forces. The enforcement approach is visual inspection by the officers. These agencies report little 

problems with violators along the corridors where shoulder use is provided. (23), (26)

Incident Response

Incident response along the facilities with temporary shoulder use is handled in a similar manner 

for all of the agencies. A typical unified response approach is deployed; this response is led by State 

police and the DOT first responders and uses typical regional response protocols. (18), (23), (24), (25), (26) 

Average response times are typical for the shoulder use facilities as with other facilities in the 
47

regions. In Virginia, the safety service patrol was increased in the corridor, particularly during the 

operating hours of the shoulder on I-66. (25) Additionally, emergency pull-out areas were installed 

along I-35W in Minneapolis to help facilitate incident response during the time period when the 

PDSLs are operational. (27) 

Training

Metro Transit, the largest transit operator in the Minneapolis-St. Paul region, uses a training 

manual along with class time, route, and safety pamphlets for training its bus operators. The 

manual includes a small section on bus shoulder use, along with a training video and on-board 

training related to the BOS operations for the drivers. Drivers are trained on the Minnesota statutes 

(http://www.dot.state.mn.us/metro/teamtransit/docs/mn_statutes_2006.pdf), the Mn/DOT 

Commissioner Order (http://www.dot.state.mn.us/metro/teamtransit/docs/draft_order_7-29-

05.pdf), the Mn/DOT Guidelines on Shoulder Use by Buses (http://www.dot.state.mn.us/metro 

/teamtransit/docs/bus_only_shoulder_guidelines.pdf), and the Mn/DOT Shoulder Operating Rules 

(http://www.dot.state.mn.us/metro/teamtransit/docs/operating_rules_on_shoulder.pdf). A copy 

of the Metro Transit Training Video is available at http://www.dot.state.mn.us/metro/teamtransit 

/visual/Training%20For%20Bus%20Drivers%202.wmv).

Costs

The installation of a temporary shoulder can be a reasonable expense when compared to the 

construction of new freeway lanes. While the initial costs to convert the shoulders on I-66 in 

Virginia are not known because of the lack of current institutional knowledge, a recent assessment 

to upgrade the lane control system along with the facility was estimated to be 7 million dollars for 

the entire 6-mi segment. While that installation is somewhat expensive, it is still much less than 

constructing 6 mi of new pavement in a congested urban area. Project costs are unknown for the 

Massachusetts projects. In Minnesota, the PDSL project cost 13 million dollars, which included a 

new pavement surface for the entire facility, including the shoulder lanes and emergency pull-out 

areas. Contrast those costs to the approximately 70,000 dollars it cost WSDOT to install a 1.5-mi 

shoulder segment on the US 2 trestle. The cost for Mn/DOT to install BOS along a freeway varies 

according to the requirements, but most installations are very reasonable, as shown in Table 1. 

Liability Issues

In the applications in the United States, no liability issues were of noted concern at the time of 

installation and deployment. One concern was broached by the American Automobile Association 

(AAA) with respect to the extension of operating hours along I-66 in Virginia. (25) When VDOT 

announced plans to extend operating hours to improve operations with longer peak periods, AAA 

expressed concern because the hours in which the shoulder would be available for emergency 

refuge in the event of an incident would be reduced even further. However, with concerted effort 

on the part of VDOT to work with AAA to address their concerns, no issues of significance have 

emerged since the extension was implemented. 
48

Table 1. Shoulder Use Installation Costs—Mn/DOT. (18)

Condition Costs Plus Signing & Striping

Shoulder width and bituminous depth are adequate. Catch 

basins do not need adjustment. Signing and striping are only 

requirements.

$1,500 per mile—Freeway

$2,500 per mile—Expressway 

Shoulder width and bituminous depth are adequate. Minor 

shoulder repairs and catch basin adjustments are needed.

$5,000 per mile—Freeway

$5,000 per mile—Expressway 

Shoulder width is adequate but bituminous depth requires a 

2-inch overlay. This assumes shoulder and roadway can be 

overlaid at the same time.

$12,000 per mile—Freeway

$12,000 per mile—Expressway 

Same as above but adjacent roadway is not being overlaid. 

Shoulder must be removed, granular base adjusted, and 

increased bituminous depth replaced.

$80,000–$100,000 per mile

Shoulder width and depth replacement are required. $42,000–$66,000 per mile for both freeway 

and expressway

Installing a 12-ft shoulder rather than a 10-ft shoulder in a 

new construction project.

$30,000 per mile for both freeway and 

expressway

Legal Issues

No specific legislation was required to implement the I-66 temporary shoulder use in Virginia. The 

implementation was under the jurisdiction of the Commonwealth Transportation Board and the Code 

of Virginia. ( (25)) The Mn/DOT deployed the BOS under the order of the Mn/DOT transportation 

commissioner. Additionally, specific Minnesota statute (169.306) was changed to address the use of 

shoulders by buses and driving rules for those buses when operating on the shoulder (169.18). (18) 

Public Outreach and Education

Initially, Mn/DOT did not implement a public outreach and education plan when deploying the BOS. 

Once the facilities were in operation, they did occasionally host a media event where a local 

celebrity challenged a transit vehicle to a race on a congested corridor with BOS during the peak 

period. The intent was to demonstrate the travel time savings and benefit to using transit in the 

corridor. These events received good media coverage and served as an educational opportunity for 

the general public. (18) Typical outreach efforts were used in the Seattle area prior to the opening of 

the US 2 shoulder lane. (26) The city of Everett, Washington, was a great proponent of the project 

because of the expected improvements for the commute out of the city. 

NCHRP/AASHTO/FHWA Domestic Scan

In November 2009, an NCHRP/American Association of State Highway and Transportation Officials 

(AASHTO)/FHWA domestic scan was completed to look at the issue of maximizing flow on existing 

highway facilities. This scan tour visited and documented several temporary shoulder use locations 

around the United States. There were members of this team from FHWA and the following State 

DOTs: Washington, Georgia, New Hampshire, Michigan, and New Mexico. The results of the scan 

team’s report are useful for development of guidance in temporary shoulder usage. 
49

Chapter Summary

Agencies need to consider a wide range of issues when determining whether shoulder use is 

appropriate for a particular corridor or region. Experience both overseas and domestically provide 

a wealth of experience from which agencies can learn to make informed decisions. From the 

European perspective, part-time shoulder use is only used during congested periods when queues 

begin to build at bottlenecks in the system. Moreover, this treatment is almost always deployed in 

conjunction with speed harmonization. The intent is to reduce the speeds along the corridor and 

smooth out driver performance and reduce the likelihood of collisions. (1) Furthermore, European 

agencies have realized both safety and mobility benefits as a result of these projects. While 

American deployments have been limited, the experience has generally been positive. However, 

safety benefits have not been conclusive. Those issues that need to be considered include design, 

traffic control devices, performance measures, potential safety benefits, maintenance concerns, 

enforcement roles and processes, incident response, training for personnel, costs, liability and legal 

issues, and public outreach and education. Careful consideration of these issues can help ensure a 

shoulder use deployment is effective without having negative impacts on safety and operations.

Another area needing further analysis is the topic of left shoulder use versus right shoulder use. 

Domestically, almost all applications of part-time shoulder use have occurred on the right side, 

while shoulder conversions to permanent lanes have tended to be more prominent on the left side. 

Each application has a different subset of design and operational considerations to analyze.
50

Chapter 4: Case Studies

Case Study: The Netherlands—Temporary Shoulder Use and Speed 

Harmonization

Overview

Facility 

• Various throughout The Netherlands. 

Operator

• NTCC and regional control centers. 

Years of Operation

• 1981–current. 

Operating Strategy Overview

• Advanced queue warning systems that utilize flashing lights and variable speed limit 

signs alert drivers of recurrent congestion, lane closures, and incidents.

• Requires extensive technological investment and monitoring activities.

• Deployment is automated based on field data and is initiated automatically based on an 

assessment algorithm, requiring no intervention by an operator.

• Only operates during time periods of congestion or when incidents occur along 

instrumented roadways.

Number of Lanes

• Applied to an entire corridor, encompassing all lanes. 

Length

• 1,000 km (620 mi) of roadway. 

Project Description

The Area

The Netherlands is home to over 16.2 million residents and 6.9 million cars, with 155 million 

vehicle miles traveled each day across its network. It covers an area of roughly 16,000 mi2. Traffic 

operations are controlled by a series of five regional traffic control centers, which are in turn 

coordinated by NTCC. (1) 

Temporary Shoulder Use

The Netherlands implemented temporary right shoulder use—also known as hard shoulder 

running or the rush hour lane—in 2003 as part of a larger program to improve use of the existing 

infrastructure. As Figure 24 shows, a gantry with lane control signals indicates when the shoulder 

is available for use. Where a shoulder lane passes through a junction and at the end of a hard 

shoulder running section, guidance information will change according to lane use. (14) 
51

Figure 24. Photo. Temporary Right Shoulder Use—The Netherlands. (36)

In addition to allowing temporary use of the right shoulder, the Dutch also deploy the use of 

traveling on a dynamic lane on the median side of the roadway. As Figure 25 shows, the left lane—

also known as the plus lane—or a narrowed extra lane provided by reconstructing the existing 

roadway while keeping the hard shoulder is opened for travel use when traffic volumes reach levels 

that indicate congestion is growing. 

Figure 25. Photo. Plus Lane in The Netherlands. (36)
52

Temporary shoulder use in The Netherlands is only deployed in conjunction with speed 

harmonization. This strategy works to reduce speeds in congested conditions in order to improve 

traffic flows and reduce the likelihood of traffic incidents. Such systems require significant 

technological development, as traffic speeds must be continually monitored and information must 

be continually transmitted throughout the entire corridor. The Netherlands’ speed harmonization 

system works through the motor control and signaling system (MCSS), an advance queue warning 

system that utilizes flashing lights and variable speed signs to alert drivers of congestion and lane 

closures. (1) 

The entire system monitors traffic speeds in the corridors it is implemented in. Should the system 

detect large drops in overall speed within a certain area, it notifies other travelers of the impending 

slow down and lowers the speed limit in incremental stages as displayed on variable speed signs 

for traffic approaching the congested area, as shown in Figure 26. This alleviates the “shock” that 

can be caused by a sudden reduction in speed, improves traffic flow, and reduces the number of 

traffic incidents as a result of congested conditions. Speed harmonization is often employed during 

severe weather conditions and in environmentally sensitive areas to reduce pollutants. 

Figure 26. Photo. Speed Harmonization—The Netherlands.

The standard speed limit is 120 km/h (75 mph) on the motorways, but posted speeds can drop to 

90 km/h (55 mph), 70 km/h (44 mph), or as low as 50 km/h (31 mph) if a shock wave or speeddrop is detected. These conditions are normally due to high volumes or incidents occurring on the 

facility. As of 2007, the MCSS system has been implemented on over 1,000 km (620 mi) of roadway 

in The Netherlands, and 61 km (38 mi) more are planned. The MCSS was first deployed in 1981.
53

Project Conceptualization

Speed harmonization is only one element of the overall transportation system for The Netherlands. 

The Ministry of Transport, Public Works and Water Management (Rijkswaterstaat) manages over 

2,000 mi of The Netherlands’ mainline roadways and operates the country’s numerous regional 

traffic control centers in addition to the NTCC. (36) The primary focus for Rijkswaterstaat is on 

maintaining high levels of customer service and ensuring trip reliability, which has led the agency 

to establish the following benchmarks: 

• Ninety-five percent of trips are completed on time.

• Trips in urban areas do not take more than twice as long in congested conditions as they 

do in normal conditions.

• Trips on all other roads do not take more than 1.5 times as long in congested conditions 

as they do in normal conditions. (37)

Speed harmonization works toward both goals of customer service and trip reliability, as it keeps 

travelers informed of current conditions and manages roadway conditions so as to maximize 

throughput and reduce travel time variability. Temporary shoulder use complements speed 

harmonization to better utilize roadways and improve trip reliability. 

Facility Management

In the Dutch national approach to congestion management, information is a primary resource in the 

overall traffic management architecture, including speed harmonization. Information is the 

backbone behind all traffic and demand management strategies in the control scheme. The NTCC 

coordinates the activities of and gathers traffic-related data from the five regional traffic control 

centers that center on major cities and operate 24 hours a day, 7 days a week. The regional traffic 

control centers are responsible for the daily operation of the congestion warning and speed 

harmonization systems. (38) The NTCC, which also operates 24-7, is the focal point for national 

traffic operations. It establishes national guidelines and procedures on traffic management, 

coordinates emergencies, communicates with other European national centers, and collects 

management information from around the country. The NTCC fosters cooperation between the 

national and regional governments to direct road users for optimal roadway performance. (1) 

Technologies Deployed

The Netherlands has used speed harmonization for many years. Some deployments have been 

implemented to promote safer driving during adverse weather conditions (such as fog), while 

others have been used to create more uniform speeds. Most recently, The Netherlands' MCSS has 

been used to reduce speed in a densely populated and environmentally sensitive area to reduce 

polluting elements. The posted speed limit of 80 km/h (50 mph) is further effectuated by an 

automated speed enforcement system, which measures average speed over a section of the 

highway, normally 2 to 3 km long. Temporary shoulder use is a more recent implementation of 

ATM, having been first implemented in 2003. Additional technologies and facilities are always 

implemented along with temporary shoulder use to help mitigate any adverse safety consequences 

the operational strategy may create, including the following:
54

• Overhead lane signs and full matrix signs.

• Emergency refuge areas with automatic vehicle detection.

• Variable route signs at junctions.

• Advanced incident detection.

• CCTV surveillance.

• Intensified incident management.

• Public lighting. (1)

Performance of System

Highway System Performance

It is estimated that facilities under the MCSS system have seen throughput increase between 4 and 

5 percent. Primary accidents decreased by 15 to 25 percent, and secondary incidents decreased by 

40 to 50 percent between 1983 and 1996. It is estimated that speed harmonization has reduced 

collisions by about 16 percent and increased throughput by 3 to 5 percent, and has reduced the cost 

of work zone traffic control. Regarding temporary shoulder use, assessment of this strategy reveals 

that its implementation has increased overall capacity 7 to 22 percent (depending on usage levels) 

by decreasing travel times from 1 to 3 minutes and increasing traffic volumes up to 7 percent 

during congested periods. (39) 

Safety and Incidents

The Dutch have seen a reduction in incidents on facilities with temporary shoulder use, as shown in 

Figure 27. Additional safety benefits may include fewer queues and shockwaves, lower travel 

speeds with harmonization, better monitoring, and swifter incident response. Temporary shoulder 

use is allowed only when speed harmonization is in effect. 

Figure 27. Graph. Incident Reductions with Temporary Shoulder Use—The Netherlands. (14)
55

Case Study: Germany—Temporary Hard Shoulder Use and Speed 

Harmonization 

Overview

Facility

• Various.

Operator

• Federal Ministry of Transport and regional traffic management centers. 

Years of Operation

• 1996–current. 

Operating Strategy Overview

• Variable speed limit signs alert drivers to reduce speeds as a result of recurrent 

congestion, lane closures, and incidents to address bottlenecks on the freeway network 

caused by these conditions.

• Temporary shoulder use designated by sign gantries with variable message signs and 

shoulder-mounted diagrammatic signs to indicate availability for use; operational when 

traffic volumes are high and the hard shoulder is strong and wide enough for use.

• Temporary hard shoulder use only deployed with speed harmonization (line control) 

when the maximum allowable speed limit is 100 km/h (62 mph) and if dynamic 

message signs are used for lane control.

• Deployment of variable speed limits is automated based on field data and is initiated 

automatically based on an assessment algorithm, requiring no intervention by an 

operator.

• Operates both between junctions and through junctions.

Number of Lanes

• Applied to an entire corridor, encompassing all lanes. 

Length

• Over 200 km of roadway currently in congested corridors across the country. 

Project Description

The Area

Germany is home to an estimated 82 million inhabitants and covers an area of about 138,000 mi2. 

Its federal motorway network is about 7,500 mi spread across 10 states. Most of these major 

highways are four- to six-lane facilities that carry average daily traffic volumes of about 49,000 

vehicles. Overall demand on the German transportation network is expected to increase by 

16 percent for passenger transport and 58 percent for freight transport by 2015. Officials hope to 

accommodate this growth with the construction of over 1,000 mi of new roadways, widening 

1,300 mi of existing roadway and constructing 717 bypasses. (16) 
56

Temporary Shoulder Use

Temporary shoulder use in Germany, also known as hard shoulder use, is only deployed in 

conjunction with speed harmonization to address capacity bottlenecks on the freeway network. In 

Germany, it provides additional capacity during times of congestion and reduced travel speeds. The 

use of the right shoulder during peak travel periods has been used in Germany since the 1990s, 

with the first deployment on the A4 near Cologne in December 1996. (12) Today, nearly 125 mi of 

temporary hard shoulders are in operation around the country. This temporary shoulder use is one 

of several traffic control systems developed by the Federal Ministry of Transport and is used in 

various locations in the country. (29) When travel speeds are reduced, signs indicate that travel on 

the shoulder is permitted, as Figure 28 shows. This installation is located on the Autobahndirektion 

Südbayern (South Bavaria) and has had the official signs added digitally for illustrative purposes. 

Figure 29 shows the complete series of signs indicating operations related to temporary shoulder 

use, including one with a supplemental speed limit indication (used when overhead gantries are not 

present). These signs and the overhead lane messages are blank when travel on the shoulder is not 

permitted. Temporary shoulder use is permitted only when speed harmonization is active and 

speed limits are reduced. 

Figure 28. Photo. Right Shoulder Use with Speed Harmonization—Germany. (13)
57

Figure 29. Illustration. Temporary Hard Shoulder Use Signs—Germany. (13)

Temporary shoulder use in Germany can either end or continue through interchanges depending 

on the bottleneck locations and overall characteristics of the corridor. Figure 30 and Figure 31

illustrate the signing and marking used when temporary hard shoulder use continues through an 

interchange. Figure 32 and Figure 33 illustrate those signs and markings used when temporary 

hard shoulder use terminates at an interchange.

Figure 30. Illustration. Signs and Markings for Temporary Hard Shoulder Use Continuation 

through Interchange—Germany. (13)
58

Figure 31. Photo. Continuation of Temporary Hard Shoulder Use through an

Interchange—Germany. (13)

Figure 32. Illustration. Signs and Markings for Temporary Hard Shoulder Use Termination 

at Interchange—Germany. (13)
59

Figure 33. Photo. Termination of Temporary Hard Shoulder Use at 

Interchange—Germany. (13)

Project Conceptualization

In response to the growing demand on its roadways, the Federal Ministry of Transport, Building, 

and Urban Affairs established a Federal Transport Infrastructure Plan to upgrade the road network 

by 2015 through major construction projects. This plan includes constructing 1,074 mi of new 

motorways, widening 1,340 mi of existing motorways, and constructing 717 bypasses across the 

country. ( (16)) In addition, the ministry has a comprehensive 5-year Programme for Traffic Control 

on Federal Motorways, which is oriented toward overall management of the federal motorway 

network. This program’s objectives are to (1) increase by 745 mi the length of motorways 

equipped with traffic control systems, (2) increase by 1,500 mi the length of motorways with 

dynamic diversion possibilities, and (3) increase by 15 the number of traffic control centers across 

the country. Both federal initiatives illustrate a national movement to upgrade and actively manage 

the motorway network for efficient operations and to enhance the mobility of the country’s citizens. 

Temporary hard shoulder use and speed harmonization are critical components of this 

management program.

The German federal government also has a policy on telematics and transport, with a primary 

emphasis on public-private cooperation. The intent is to define specific responsibilities that are 

best handled by the public sector, those that are best handled by the private sector, and those that 

can best be accomplished by public-private partnerships. This policy recognizes the strengths of 

the private sector in some arenas and acknowledges that some activities can be undertaken only by 
60

governmental agencies and should remain under public control. The federal government owns the 

federal motorways and highways and finances their construction, maintenance, and telematic 

infrastructure deployment, while the individual states are responsible for maintenance, operations, 

traffic safety, traffic regulations, and financing of the planning and operational activities for the 

network. 

Facility Management

At the regional level, German states establish freeway operation programs for their motorway 

networks with two primary objectives. The first objective is to maintain or increase safety by 

harmonizing traffic flow, providing hazard warnings to motorists, and providing dynamic in-vehicle 

information on traffic conditions to users. The second objective is to maintain and improve 

mobility, which is achieved through the optimal use of the existing network capacity and the use of 

various operational strategies to temporarily increase road capacity. (40) 

Regional traffic management centers, like the Traffic Center Hessen, have established a proactive 

traffic management approach. This approach is a comprehensive framework that encompasses 

benchmarking of network performance; deploys and maintains various traffic management 

strategies to meet the aforementioned objectives; incorporates data management, traffic analysis, 

and forecasting to evaluate and assess the impacts of those strategies; and facilitates the 

implementation of innovations to enhance mobility. Temporary use of hard shoulders and line 

control are two tools in this proactive congestion management toolbox.

Technologies Deployed

Components typically installed with the required regulatory signs include:

• Overhead gantries.

• Dynamic speed limit displays.

• Dynamic message signs.

• Roadway sensors.

• CCTV cameras. 

Performance of System

Highway System Performance

Overall, Germany has seen considerable benefits from the deployment of temporary hard shoulder 

running and speed harmonization. These benefits include a travel time reduction of up to 

20 percent, a temporary increase of up to 25 percent in freeway capacity, and a high motorist 

acceptance of variable traffic signs given reasonable speed limits are displayed for speed 

harmonization. Temporary shoulder use affords congested motorways with higher throughput, as 

shown in Figure 34. The addition of the third lane in the form of temporary shoulder use, while 

slightly decreasing speed and initially reducing volumes on the motorway, actually delays the onset 

of congestion and breakdown and increases the overall throughput on the facility. Similar 

operational improvements are realized as a result of speed harmonization, with breakdown flow 

under breakdown conditions being reduced, as shown in Figure 35. 
61

Figure 34. Graph. Speed-Volume Relationship of Temporary Shoulder Use—Germany. (13)

Figure 35. Graph. Flow Impacts of Speed Harmonization—Germany. (41)
62

Safety and Incidents

The safety benefits realized through the use of speed harmonization are significant. Facilities with 

speed harmonization have seen a reduction of up to 29 percent in accidents with personal damage, 

a reduction of up to 27 percent in accidents with heavy material damage, and a reduction of up to 

3 percent in accidents with light material damage, as shown in Figure 36. 

Figure 36. Graph. Safety Benefits of Speed Harmonization—Germany. (40)

Case Study: Great Britain—Temporary Shoulder Use System

Overview

Facility

• M42 Motorway (J3A to J7).

Operator

• Highways Agency.

Years of Operation

• 2006–current.

Operating Strategy Overview

• Variable speed limit signs alert drivers to reduce speeds as a result of recurrent 

congestion, lane closures, and incidents.
63

• Temporary shoulder use designated by sign gantries with dynamic message signs to 

indicate availability for use.

• Temporary shoulder use deployed only when speed limits are reduced (initially to 50 

mph).

• Deployment of variable speed limits is automated based on field data and is initiated 

automatically based on an assessment algorithm, requiring no intervention by an 

operator.

• Only operates (1) during time periods of congestion or when incidents occur along 

instrumented roadways, and (2) between junctions, requiring users to exit at each 

junction and reenter the roadway beyond.

• Emergency refuge areas provided for use when vehicles break down.

Number of Lanes

• Applied to an entire corridor, encompassing all lanes. 

Length

• 11 mi of roadway currently with plans to expand to other congested corridors. 

Project Description

The Area

As with other countries across Europe, the United Kingdom (UK) now faces a number of new 

challenges regarding transportation and mobility. Trends in traffic growth predict that volumes 

will increase by 29 percent by the year 2010, and with increased volumes comes increased 

congestion on the transportation network. Estimates are that non-recurrent congestion in the form 

of incidents (25 percent) and construction (10 percent) account for 35 percent of congestion. (42) 

Active Traffic Management (ATM)

Introduced in 2001 by the Minister of Transport, the M42 ATM pilot is an operational strategy 

intended to provide reliable journeys, reduced recurring and non-recurring congestion, and 

enhanced information to drivers. (43) It is a direct response to the road users’ demands for better 

service within the realistic limitations of widening and expanding the roadway network. Building 

on advancements in technology and experience from across the globe, this pilot project works to 

make the best use of the existing capacity on the segment of M42 between junctions 3A and 7. The 

ATM pilot also provides additional capacity during periods of congestion or incidents. The pilot 

project combines the strategies of speed harmonization and temporary shoulder use. To ensure 

safe operations of the temporary shoulder use, emergency refuge areas are spaced at 1,640-ft

intervals along the shoulder (as shown in Figure 37), and emergency call boxes are provided at 

each refuge area (as shown in Figure 38).
64

Figure 37. Photo. Emergency Refuge Area on Facility with Active Traffic Management—

England. 

Figure 38. Photo. Emergency Call Box on Facility with Active Traffic Management—England. 
65

The roadway provides traditional information to travelers as seen on other motorways across the 

region. Under such conditions, all normal rules apply. However, information provided to travelers 

changes during periods of recurring congestion or incidents depending on whether or not the hard 

shoulder is open for travel. In both cases, gantries with lane control signals and dynamic message 

signs indicate reduced speed limits and the availability of the hard shoulder for travel use rather 

than for emergency refuge only. Overall benefits include increased capacity; enhanced journey 

reliability; reduced driver stress, number and severity of crashes, traffic noise, emissions, and fuel 

consumption; and improved driver behavior. (44)

Project Conceptualization 

In 2004, the Department for Transport established a long-term strategy for a modern, efficient, and 

sustainable transport system that is supported by a high level of investment. Acknowledging that 

transportation is vital to the economy and quality of life, the strategy focuses on providing a 2030 

transportation network that can meet the challenges of a growing economy and an increasing 

demand for travel while achieving environmental objectives. Three themes support this strategy: 

(1) a sustained investment in the transportation network over the long term; (2) continued 

improvements in transportation management to maximize the benefits of public spending; and (3) 

planning for the future and considering new and innovative approaches to improving 

transportation. Underlining these themes is the objective to balance the need to travel with the 

need to improve quality of life. The ATM is a key component of the agency’s approach to meeting 

its long-term strategy for its transportation network. (45)

A primary goal for improving transportation across the UK is related to safety—which is an 

acknowledged contributor to roadway congestion. The national goal, which has been in place since 

2000, is to maintain the network in a safe and serviceable condition. A continuous review of 

measures to improve roadway and work zone personnel safety through engineering and design 

improvements are key activities related to this goal. Specific numbers that the Highways Agency is 

working to meet include a 33 percent reduction in the number of deaths or severe injuries in 

motor-vehicle related accidents, a 10 percent reduction in the number of minor injuries – both of 

which will contribute to a 50 percent reduction in child casualties. (46) 

Facility Management

The national focal point for congestion management in the UK is the NTCC. At this information hub, 

NTCC staff monitor a network of over 1,730 CCTV cameras and 4,450 traffic sensors 24 hours a day, 

365 days a year. Staff members review the network and deliver vital information to the news 

media and other operational partners including the police and the Highways Agency traffic officer 

service. They also display real-time messages on the 350 DMS placed at strategic points on the 

motorway network.

The NTCC coordinates and is interconnected with seven regional control centers across the 

country. These centers monitor and maintain the roadway network within their jurisdiction and 

are the first line of control regarding congestion management. If minor incidents occur, the 

regional centers initiate appropriate responses related to incident and congestion management and 

report information to the NTCC regarding the incident. For major incidents, actions are 
66

coordinated with the NTCC as needed to optimize the remaining capacity and to minimize the 

duration and impact of the incident on the entire motorway network and the adjacent local road 

system. The West Midlands Traffic Control Center in Birmingham is responsible for operating the 

ATM system on the M42 as part of its overall duties.

Technologies Deployed

The ATM project on the M42 has numerous technological components that ensure its successful 

operation. In addition to the traffic sensors, CCTV cameras, and DMS deployed on the roadway 

network as part of the regional traffic control center, the completed system includes the installation 

of the following: 

• Lightweight gantries.

• Lane control signals.

• Dynamic speed limit signals.

• Dynamic message signs.

• Digital enforcement technology.

• Closed-circuit television cameras.

• Enhanced lighting.

• Roadway sensors.

• Emergency roadside telephones.

• Emergency refuge areas. (43)

Performance of System

Highway System Performance

Overall, traffic conditions on the M42 have become smoother and more consistent since the 

implementation of ATM. Weekday travel times have reduced in variability by 27 percent, and 

capacity has increased by an average of 7 to 9 percent when hard shoulder running is in effect. 

Travel times have improved by 24 percent in the northbound direction and 9 percent in the 

southbound direction during peak periods as a result of the speed harmonization deployment. (47) 

Moreover, the travel time variability has been reduced by 22 percent to 32 percent since 

deployment, allowing drivers to more accurately predict their journey times. These trends are 

shown for both winter and summer seasons despite the increase in demand experienced during the 

summer season. Additionally, the ATM on the M42 improved the distribution of traffic across the 

travel lanes and has not had an adverse effect on traffic in the surrounding areas.

Safety and Incidents

Overall, traffic operations on the M42 have improved, with traffic congestion and the speed

differential between lanes being reduced. Furthermore, there is a higher occurrence of free-flow 

conditions with headways greater than 5 seconds. During the first year of operation, a limited 

crash analysis indicated that accidents along the corridor in the ATM section decreased from 5.08 

per month to 1.83 per month. (48) 
67

Other Impacts

Initial vehicle emission and air quality measurements indicate that vehicle emissions for carbonmonoxide, particulate matter, carbon-dioxide, and oxides of nitrogen have dropped between 4 and 

10 percent and fuel consumption has dropped by 4 percent since deployment. Noise reduction 

along the corridor has also been measured between 1.8 dB(A) and 2.4 dB(A). (48)

Case Study: Virginia—I-66 Temporary Shoulder and HOV Lanes

Overview

Facility

• I-66 (U.S. 50 to I-495).

Operator

• Virginia Department of Transportation.

Years of Operation

• 1992–current . 

Operating Strategy Overview

• Use of rightmost shoulders by general purpose traffic only during peak periods 

Monday–Friday (eastbound, 5:30 a.m.–11:00 a.m.; westbound, 2:00 p.m.–8:00 p.m.).

• Installation was as a result of the adaptation of leftmost general purpose lane to HOV-2 

lane concurrent with opening of shoulder lane (eastbound, 5:30 a.m.–9:00 a.m.; 

westbound, 3:00 p.m.–7:00 p.m.).

• Advance signage and traffic control signaling provide travelers information of 

operations, including large signs alerting drivers to nine emergency refuge areas.

• Opening of the shoulder lane during traffic incidents/construction.

Number of Lanes

• One HOV-2 lane, captured from interior-most general purpose lane, operational 

concurrent with opening of exterior shoulder for use by general purpose traffic.

Length

• 6.5 mi of dual HOV/Shoulder Lane operations.

Project Narrative

The Area

As the primary highway connecting Washington, D.C. (population 600,000), and Northern Virginia 

(population 2,400,000), I-66 suffers heavy traffic throughout the Fairfax County section. Although 

the corridor features concurrent metro-rail service (Washington Metro Orange Line, operating 

between Vienna and western Arlington County), the freeway’s three lanes in each direction are 

often overtaxed. 
68

Temporary Shoulder Use

Built in 1964, the segment of I-66 between U.S. 50 and I-495, where the case study HOV/shoulder 

lane combination is operational, includes three main lanes in each direction. Starting in 1992, the 

shoulder was opened to peak-period, peak-direction general purpose traffic, allowing the leftmost 

lane to operate as an HOV lane (illustrated in Figure 39). This lane provides continuity to HOV 

lanes that continue on I-66 west of U.S. 50 for an additional 15 mi to VA-234 (49). The cross-section 

west of U.S. 50 includes a static HOV lane (interior) and three general purpose lanes (exterior), as 

shown in Figure 40. 

In the combined HOV/shoulder lane segment (hereafter referred to as HOV/SL), three travel lanes 

and one shoulder are present for the entire segment with a posted speed limit of 55 mph. When 

shoulder lanes are active, four emergency refuge areas (eastbound) and five refuge areas 

(westbound) provide accommodation for breakdowns and enforcement activities. Additionally, 

collector/distributor roads (barrier separated from main lanes) provide access to and from the 

corridor’s three ingress/egress ramps (eastbound) and four ingress/egress ramps (westbound). 

The shoulder lanes and C/D roads can be seen in Figure 41. As shown in the cross-section in Figure 

42 and Figure 43, the general purpose lanes are 12-ft wide, the interior shoulders are 8- to 12-ft 

wide, and the exterior shoulders are 11-ft wide. 

Figure 39. Photo. I-66 Peak Period Shoulder Use—Virginia (50). 
69

Figure 40. Photo. I-66 HOV Lanes, West of HOV/SL Portion—Virginia (50). 

Figure 41. Photo. I-66 HOV/SL Portion—Virginia (50). 
70

Figure 42. Illustration. I-66 HOV/SL Lane Plan View—Virginia (50). 

Figure 43. Illustration. I-66 HOV/SL Typical Cross-Section—Virginia (50). 
71

Project Conceptualization 

I-66 has a storied history. Originally conceived in 1956 and designed in the 1960s, I-66 was one of 

the initial highway construction projects to be successfully sued on the grounds of lacking an 

environmental impact statement (despite the approval and design occurring prior to the enactment 

of the National Environmental Policy Act). The HOV/SL was constructed prior to this lawsuit, but in 

1972, the U.S. Court of Appeals required the U.S. Department of Transportation to halt construction 

and conduct an environmental impact statement specifically for the portion east of I-495. The end 

result was a four-lane freeway (two in each direction) between Washington, D.C., and I-495, with 

HOV-2+ required for the peak period/peak-direction portion of the freeway between I-495 and 

Rosslyn (although single occupant vehicle (SOV) travel to/from Dulles airport is permitted) (51). 

This cross-section allows the HOV/SL portion to have an interesting design—two separate ramps to 

I-495 from I-66 directly accessible from both the HOV lane and the shoulder lane, as shown in 

Figure 44. Lane balancing is not an issue, given the constrained design within the beltway.

Figure 44. Photo. I-495, Viewing Dual Entrance Ramps from I-66—Virginia.

Facility Management

Whereas the shoulder lanes are open to general purpose traffic, the HOV lane is open to all vehicles 

meeting either two-person restrictions or permitted hybrid vehicles. An overhead sign enables a 

downward pointing green arrow when the SL is active, and a red X appears when the shoulder has 

been recovered, as seen in Figure 16. To respond to the need for incidents and breakdowns, 

emergency refuge areas have been constructed since the implementation of the facility. (52) 

Furthermore, the operational hours of the shoulder lanes have changed since 1995 to respond to 
72

changing traffic conditions. Peak period conditions often extended beyond the original 10:00 a.m. 

eastbound threshold, and prior to the 3:00 p.m. westbound initialization. As a result, VDOT 

extended the operational times to 11:00 a.m. and 2:00 p.m., respectively. (53), (54) 

Performance of System

Highway System Performance

In 2007, typical traffic volumes during the eastbound HOV/SL hours ranged from 19,500 to 27,000 

vehicles, with 21,000 to 25,000 vehicles westbound. These volumes compare with 190,000 average 

annual daily traffic (AADT) for the corridor in this segment. Truck volumes are low (approximately 

2-3 percent), as are bus volumes (1 percent) within the HOV/SL portion of I-66. Within the HOV/SL 

segment, morning volume-to-capacity (V/C) ratios fell between 0.90 and 1.00 (eastbound), 

indicating at capacity, heavy volume usage. In the westbound direction, LOS F conditions typically 

resulted, with V/C ratios between 0.83 and 1.01 (suggesting the backward-bending portion of the 

V/C curve, whereby saturated conditions depress both volumes and speeds). (33) 

Safety and Incidents

Based on a safety analysis using negative binomial regression models and crash data from 2002 to 

2004, researchers concluded that there was no evidence that the HOV/SL managed-lane strategy 

had a statistically significant effect on crash frequency during peak hours. As the authors of the 

study commented, “A typical factor, high AADT volume, and a natural causal factor, light conditions, 

especially combined with motorists’ aggressive lane change behaviors in merging and diverging 

areas, are presumably major factors influencing crashes in the study area,” and not the effect of the 

SL operations directly. (33)

Case Study: Minnesota—Priced Dynamic Shoulder Lanes

Overview

Facility

• I-35W, north of 42nd Street to Downtown Minneapolis.

Operator

• Minnesota Department of Transportation.

Years of Operation

• 2009–current.

Operating Strategy Overview

• Use of leftmost shoulder provides MnPASS Express Lane service during certain times 

when traffic along the general purpose lanes is congested.

• Transit vehicles, carpools, and MnPASS customers (SOV) are able to use the converted 

shoulder lane when operational.

• Transit vehicles and high-occupancy vehicles operate at no charge in the PDSLs. 

MnPASS customers (SOV) pay the displayed fee for shoulder access to the PDSL.

• Prices for MnPASS customers are set to ensure free-flow travel.
73

• Installation was a conversion of a right shoulder bus-only-shoulder operation to a left 

PDSL and was included as part of a larger Urban Partnership Agreement project for 

Mn/DOT.

Number of Lanes

• One left shoulder lane.

Length

• Approximately 2.5 mi of PDSL.

Project Description

The Area

IH-35W is a major north-south corridor that connects the southern suburbs and downtown 

Minneapolis, Minnesota. Congestion is extensive along the corridor and increases with proximity to 

downtown. Until the deployment of PDSLs and high-occupancy toll lanes on the facility, the right 

shoulder was used for BOS operations to provide reliable transit trips into the city. 

Priced Dynamic Shoulder Lanes

The Mn/DOT incorporated priced dynamic shoulder lanes along I-35W to improve traffic flow 

along the corridor using transit and tolling. The PDSLs connect with approximately 10 mi of 

additional new MnPASS lanes along the corridor. This project, along with the addition of two new 

transit stations, is part of a partnership between the local, State, and Federal Government funded 

through the U.S. Department of Transportation’s Urban Partnership Agreement. The MnPASS lanes 

provide a new option on I-35W during peak periods.

The PDSLs are deployed along with variable speed limits across the general purpose lanes on 

I-35W. As shown in Figure 45, sign gantries are located approximately every 1⁄2 mi along the 

section of freeway. These gantries incorporate traditional guide signs along with dynamic speed 

limit panels over the general purpose lanes. Over the PDSL, regulatory signs provide information 

on the hours of operation and the MnPASS restrictions and toll rates for access. The width of the 

PDSL varies from 17 ft to 19 ft between the left median barrier and the edgeline striping for the 

leftmost general purpose lane. 

Figure 45. Illustration. PDSL on I-35W—Minneapolis, Minnesota. (27)
74

Project Conceptualization

The PDSLs are part of a larger congestion relief program along I-35W. In addition to the PDSLs, 

additional MnPASS lanes were installed along with two new park-and-ride lots in the corridor. New 

electronic signs were installed every 1⁄2 mi between 42nd Street and downtown Minneapolis to 

provide real-time information to help motorists make informed decisions about their commute and 

the availability of the PDSLs. Lane control signals located over the PDSLs indicate whether or not 

the lane is open to users, and DMS panels on the regulatory signs display the MnPASS toll for SOV 

access to the lanes. As part of this project, emergency refuge areas were also installed off the right 

shoulder to facilitate breakdowns and incident management. The entire facility, including the 

general purposes lanes, was resurfaced as part of this project. The PDSL portion of the project cost 

13 million dollars, including the resurfacing. Unlike BOS elsewhere in the region, speeds on the 

PDSL can remain at free-flow freeway speeds to optimize travel time savings.

Facility Management

When operational, the left shoulder is available to all transit vehicles, carpools, and MnPASS 

customers. Transit and carpools are able to use the PDSL for free, while MnPASS vehicles with only 

one occupant are required to pay a fee to access the PDSL. All tolls are collected electronically, and 

there are no tollbooths on the facility. Incident response along the facility is primarily handled by 

Minnesota State Police and FIRST. 

Technologies Deployed

In addition to the traditional ITS components of cameras and loop detection, Mn/DOT added sign 

gantries spanning the entire facility, with variable speed limit panels, lane control signals, and DMS 

panels for toll display. 

Performance of System

Highway System Performance

Since the deployment of the PDSLs is very recent, extensive performance statistics are not available. 

Mn/DOT personnel state that the lane is working very well and is operating as planned. The full 

impact of the shoulder lane will occur during 2010 when the Crosstown Project is completed.

Safety and Incidents

As with system performance, safety statistics are not available at this time. However, Mn/DOT 

personnel believe that the facility is operating safely and as planned.

Case Study: Massachusetts—Shoulder Lane Use

Overview

Facility

• I-93: Exit 41 to Exit 47 from Wilmington to Methuen.

• SR 3: Exit 15 to Exit 12.

• I-95: Exit 12 to Exit 20.

• I-93: Exit 1 to Exit 4 (12 mi).
75

Operator

• Massachusetts Department of Transportation (MassDOT), Massachusetts State Police, 

and Commerce Insurance Courtesy Patrol.

Years of Operation

• 2002–current.

Operating Strategy Overview

• Use of rightmost breakdown lane (shoulder) by general purpose traffic only during peak 

periods Monday–Friday. Hours of operation vary from 5:00 a.m.–10:00 a.m. in the 

morning and 3:00 p.m.–7:00 p.m. in the evening depending on the facility.

• Post-mounted signs in yellow and white provide information to drivers on breakdown 

lane availability. The DMS are being installed along I-93 in the northern section that will 

also be used to provide breakdown lane availability. 

• Rumble strips, scored concrete, and block pavers were removed during installation.

• Emergency pull-out areas are located approximately every 1⁄2 mi along deployment 

locations.

• Heavy trucks are prohibited from using the breakdown lane as a travel lane during 

operational periods.

Number of Lanes

• One right shoulder.

Length

• 45 mi of breakdown lane use on four facilities.

Project Description

The Area

The facilities where breakdown lane use is operational during the peak travel periods are roadways 

in the Boston area that provide critical access to the region. Congestion on these facilities was to 

the point where traffic was at a standstill and drivers were taking the initiative to use the shoulder 

as a travel lane despite restrictions. 

Breakdown Lane Use

The objective of opening the breakdown lanes to general purpose traffic during peak periods was 

to increase capacity. The maximum allowed speed on the shoulder is 65 mph (60 mph on SR 3), 

which is the posted speed for the general purpose lanes. A minimum of 10-ft shoulder width is 

required for the breakdown use operations, with 12 ft being the desired shoulder width. For each 

of the projects listed, MassDOT treated the deployment as a traditional widening project. To that 

end, drainage features were moved to the new edge of pavement, and guardrails and fixed object 

shielding were moved accordingly. Emergency pull-off areas were installed approximately every 

1⁄2 mi along the facilities where breakdown lane use was deployed to facilitate incident management 

and response. The shoulders were resurfaced as part of these projects as well. Figure 46 shows the 
76

start of the breakdown lane use along I-93. A regulatory sign indicates the hours of operation and 

user restrictions.

Figure 46. Photo. Breakdown Shoulder Use on I-93—Massachusetts. (23)

Project Conceptualization

With each deployment, MassDOT has to seek approval from FHWA to implement the strategy as a 

temporary measure until funding and approval are obtained for widening. The intent is for these 

facilities to be temporary in nature and not a permanent fixture for long-term capacity provision. 

The portion of I-95 with the breakdown lane use is currently in the construction phase of a project 

that will add a general purpose lane, at which time the shoulder use will be terminated. Bridges 

along that roadway that are being widened will have enough width to add another lane at a later 

date and still provide a shoulder for breakdown use. SR 3 is at the preliminary and environmental 

state of project approval for widening, which when completed will add a general purpose lane and 

terminate the temporary use of the breakdown lane as a travel lane. 

Facility Management

The MassDOT oversees the general operation of the breakdown lane use in the Boston area. The 

Massachusetts State Police enforces the operational strategy, and the Commerce Insurance 

Courtesy Patrol provides roadside assistance in the corridors. Incident response along the facilities 

is typical of that across the region, with a unified response manual guiding procedures. Agencies 

involved include MassDOT, local fire departments, local police departments, environmental 

services, and other agencies with varying responsibilities for incident management. 
77

Technologies Deployed

Some sensors are located within the I-93 corridor, along with cameras and overhead DMS. Most of 

these technologies existed prior to the deployment of the breakdown lane use. The DMS are 

currently being installed on the northern section of I-93 to facilitate user information.

Performance of System

Highway System Performance

The MassDOT does not maintain any specific measures of effectiveness for the breakdown shoulder 

use. In general, there has been a definite improvement in travel speeds along these corridors, 

though specific improvements are difficult to track because of the lack of complete deployment of 

devices in the field for data collection purposes. 

Safety and Incidents

In general, MassDOT has seen no significant change in crash rates along these facilities with 

breakdown lane use operational. However, crash statistics are difficult to assess since crash data 

and crash locations do not really indicate whether a crash is in the breakdown lane or not. 

Case Study: Washington—State Route 2, Temporary Shoulder Use 

Overview

Facility

• US 2, eastbound direction of trestle.

Operator

• Washington State Department of Transportation.

Years of Operation

• 2009–current.

Operating Strategy Overview

• Use of rightmost shoulder deployed during evening peak period to alleviate congestion 

on the trestle.

• All vehicles allowed to use the facility during operational hours.

Number of Lanes

• One right shoulder.

Length

• Approximately 1.55 mi.

Project Description

The Area

This particular facility is a congested location, as the trestle serves as a merge point for eastbound 

traffic coming from the Everett city center and high volumes from northbound I-5. While the 

capacity of I-5 was recently improved and HOV lanes were added to the facility, the previous I-5 
78

bottleneck shifted from 526 to the Snohomish River Bridge—the US 2 trestle. Even the addition of 

an auxiliary lane on I-5 did not reduce congestion in the area. 

Temporary Shoulder Use

The WSDOT saw the potential to alleviate congestion on the trestle by opening up the right 

shoulder during the evening peak. The objective of the project was to improve travel times, reduce 

the impacts of the bottleneck at the trestle, and relieve the congestion at a critical interchange in the 

region. All vehicles are allowed to use the right shoulder of the US 2 trestle in the eastbound 

direction during the evening peak. As shown in Figure 47, the skip striping indicates to the user 

that the shoulder is open for travel. Hours of operation are Monday–Friday, 3:00 p.m.–7:00 p.m., 

with a maximum allowable speed of 60 mph on the trestle. 

Figure 47. Photo. US 2 Shoulder Use—Everett, Washington. (55)

Project Conceptualization

The US 2 trestle is a highly congested corridor in the Seattle region. The WSDOT provides 

temporary use of the right shoulder in the evening peak to alleviate some of the congestion. The 

restriping deployed allows for three different movements on the trestle to remain in their own 

lanes when shoulder use is allowed. Each destination off the bridge (SR 204, 20th Street SE, and US 

2 EB) can be reached from a separate lane when the shoulder use is allowed, eliminating the need 

for weaving and shared lane use. The intent of WSDOT is for this treatment to be a permanent one 

for the near future. 

Facility Management

The WSDOT restriped the trestle to provide adequate space for the shoulder use. Figure 48 and 

Figure 49 show the cross-sections before and after the restriping, respectively. During the 
79

restriping project, one barrier had to be minimized to allow for a wider shoulder on the trestle. 

Regarding traffic control devices, a typical skip strip and solid edgeline strip were used, and one 

overhead sign was added to mark the Homeacre Road exit. No lane control signals are used on the 

trestle. Shoulder-mounted or barrier-mounted regulatory signs, which are manual flip signs, are 

posted every 1,200 ft. One display reads “SHOULDER OPEN TO TRAFFIC,” while the closed version 

reads “SHOULDER CLOSED.” The WSDOT personnel can flip these signs in the event of an incident 

on the trestle or when it is closed for log removal in the river. The DMS signs on I-5 can be used to 

provide traveler information to those drivers destined for the US 2 trestle.

Figure 48. Illustration. US 2 Trestle Original Cross-Section—Everett, Washington. (55)

Figure 49. Illustration. US 2 Cross-Section for Shoulder Use—Everett, Washington. (55)
80

Technologies Deployed

No unique ITS technologies were deployed as part of this shoulder use project. 

Performance of System

Highway System Performance

The primary performance measure for the trestle is travel time. After deployment, delay in this 

area was reduced from 8-10 minutes to 1-2 minutes on the facility. Travel times are much more 

reliable for this commute, and throughput on the access ramps has increased. The average speed 

on US 2 after implementation of the shoulder use and ramp metering on I-5 has increased from 

10 mph to 37 mph, which is close to the maximum feasible of 42 mph because of ramp curvature.

Safety and Incidents

It is too early to confidently assess the safety improvements along the trestle. Anecdotal evidence 

provided by WSDOT personnel indicate that collisions at the conflict point where the roads merge 

on the trestle have been reduced. It is difficult to measure the true impact of the shoulder use since 

its deployment coincided with ramp metering on I-5, which feeds the US 2 trestle.

Chapter 5: Final Remarks

This report was developed to summarize the implementation of safety shoulders as travel lanes as a 

method to increase the efficient use of highway capacity. Its purpose is to provide a succinct 

overview of efforts to use left or right shoulder lanes as temporary or interim travel lanes. As part 

of this summary, information related to the impact of shoulder usage on highway safety and/or 

accidents during operations was reviewed as well. The report provides critical information that the 

FHWA can use to formulate guidance for agencies on providing temporary shoulder use as a means 

of increasing roadway capacity. The study that generated this product was conducted at the 

request of Congress through the 2008 Technical Corrections Act. 

Agencies need to consider a wide range of issues when determining whether shoulder use is 

appropriate for a particular corridor or region. Experience both overseas and domestically 

provides a wealth of experience from which agencies can learn to make informed decisions. From 

the European perspective, temporary shoulder use is only used during congested periods when 

queues begin to build at bottlenecks in the system. Moreover, this treatment is almost always 

deployed in conjunction with dynamic lane control signing and speed harmonization. Furthermore, 

European agencies have realized both safety and mobility benefits as a result of these projects. 

While American deployments have been limited, experience has been positive, though safety 

benefits have not been conclusive. The issues that need to be considered include design—such as 

the treatment at interchanges and auxiliary lanes, drainage, emergency refuge areas, rumble strips, 

and ITS components; traffic control devices; and operational and safety performance measures. In 

addition, maintenance concerns, enforcement roles and responsibilities, incident response 

procedures, personnel training, costs, liability and legal issues, and public outreach and education 

are issues that should be examined. Careful consideration of these issues can help ensure that a 

shoulder use deployment is effective without having negative impacts on safety and operations. 
81

The following results can be taken away from this summary:

• The use of buses on shoulders has generally significantly benefited transit trip time 

reliability in those corridors where it has been implemented.

• There have been shoulder use projects that have shown bottleneck relief at spot 

locations.

• Incident data provided from the U.S. seems to be inconclusive at this point. There are 

safety benefits provided from the European applications. However, the shoulder use is 

only a part of a much larger investment in ATM technology and resources to manage 

them.

• There have been longer incident clearance times in areas that don’t have shoulders 

available to move incidents off the highway. Also, responders don’t have the benefit of 

traveling the shoulder to reach the incident scene.

• European usage of hard shoulder running has always been accompanied by additional 

ATM strategies such as dynamic lane control signals and variable speed limits. These 

additional support strategies have generally been lacking in U.S. applications.

As a result of the information gained from this study, consideration should be given to the 

following:

• FHWA should consider developing clearer agency guidance on the use of shoulders. This 

would need to be a joint effort from the Offices of Infrastructure (Design), Safety, and 

Operations (including how the MUTCD relates to shoulder use lanes). The lack of 

existing U.S. performance data would also point to the need for more research in this 

area.

• Hard shoulder running was one of the ATM strategies recommended for 

implementation in the U.S. from a recent international scan. As FHWA and AASHTO 

develop guidance on ATM, they should clarify guidance on temporary shoulder usage. 

This would include comparing the differences in current U.S. usage to that of the 

European countries.

• Research and modeling for temporary shoulder use is lacking at this time. This could be 

covered in research being developed for the ATM program.

• The results of the NCHRP/AASHTO/FHWA Domestic Scan on Maximizing Flow on 

Existing Highway Facilities should be considered in the development of shoulder use 

guidance. 

83

Acknowledgements

This study was conducted in cooperation with the staff from the Federal Highway Administration 

(FHWA), Battelle Memorial Institute, and other agencies across the United States. Greg Jones—

Regional Transportation Operations Specialist with the FHWA Resource Center—served as the 

project director and provided guidance throughout the study. Special thanks are also extended to 

the following organizations for their participation in case study interviews: Massachusetts 

Department of Transportation, Minnesota Department of Transportation, Virginia Department of 

Transportation, and Washington State Department of Transportation.
84

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Department for Transport, 2004.

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http://www.dft.gov.uk/stellent/groups/dft_about/documents/divisionhomepage/031259.hscp.

46. Tailor, P. Journey Time Reliability and Network Monitoring. London, England : Highways Agency, 

Department for Transport, June 2006. Presentation to Planning to Congestion Management Scan 

Team.

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Six Months. London, England : Highways Agency, Department for Transport, 2007.

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Agency, Department for Transport, 2008.

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Lanes, Pricing, and BRT. Federal Highway Administration. Houston, TX : U.S. Department of 

Transportation, 1995. http://ops.fhwa.dot.gov/publications/12hovsysconf/.

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Research. Texas Transportation Institute. College Station, TX : s.n., 2009. Technical Report for 

Mn/DOT.

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Study. Fairfax, VA : Virginia Department of Transportation, 2003. 

http://www.infoi66.com/PurposeandNeedDocument.pdf.

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88

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Appendix A: Interview Questions for Agency Representatives

1. What facilities have had shoulder use either in the past or currently?

2. What was the intent of the implementation (goals & objectives)?

3. Were other operational strategies evaluated prior to identifying shoulder use as the 

alternative to deploy?

4. What are the specifics of that operation?

a. Facility name/number, city

b. Date implemented

c. Date terminated (if applicable)

d. Length of implementation

e. Allowed vehicles

f. Operating partners

g. Conditions associated with implementation: Is this an interim treatment until 

future widening occurs? Are speeds restricted or other conditions changed from 

the prior condition?

5. Operational hours (part-time vs. permanent) 

6. What is the maximum speed allowed for the shoulder lane?

7. What are the geometric features of the implementation?

a. Cross-sectional details, including shoulder width

b. Treatment at interchanges

c. Handling of inlets (if applicable)

d. Handling of existing rumble strips (if applicable)

e. Guardrail and fixed object shielding / adjustments (if applicable)

8. What traffic control devices are part of the implementation?

a. Pavement markings

b. Overhead signs and signals

c. Ground-mounted signs

9. What are the ITS-related elements of the implementation?

10. What performance measures are associated with the facility and how are they used?

a. Specific measures of effectiveness

b. Who is responsible for monitoring?

11. What were the costs associated with implementation?
90

12. How is the facility enforced?

a. Who is responsible?

b. What are the related fines?

c. What is the enforcement approach?

13. How is the facility maintained?

a. Who is responsible?

b. Other specific 

14. How are incidents within the facility handled?

a. Who is responsible?

b. What is the average response time?

c. Are there unique strategies deployed here that are not deployed elsewhere in 

the region?

15. What is the overall evaluation of the implementation?

a. Overall safety experience (crashes / severity)

b. Operational experience (travel speeds / delay)

c. In-service compliance rates

16. What, if any, liability issues or concerns posed a problem with the implementation of 

shoulder operations?

17. Were their impacts with oversize and/or overwidth vehicles? How were they 

addressed?

18. Was there a public outreach or education component to the deployment?

19. Was any legislation required to enable the strategy? 

20. Are there any issues with compliance or return to traditional operation on adjacent 

sections or on other local facilities that do not permit emergency shoulder/breakdown 

lane use as peak period travel lanes?
Contact Information

For additional information on this report, contact:

Federal Highway Administration

Resource Center

Mr. Gregory M. Jones

404- 562-3906

gregm.jones@dot.gov

Beverly T. Kuhn, Ph.D., P.E.

Texas Transportation Institute

3135 TAMU

College Station, TX 77843-3135

979-862-3558

b-kuhn@tamu.edu

Federal Highway Administration

1200 New Jersey Avenue SE

Washington, DC 20590

May 2010

Publication # FHWA-HOP-10-023