Incorporating 

Travel-Time 

Reliability into 

the Congestion 

Management 

Process:

A Primer

February 2015
Quality Assurance Statement

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

Government, industry, and the public in a manner that promotes public understanding. 

Standards and policies are used to ensure and maximize the quality, objectivity, utility, 

and integrity of its information. FHWA periodically reviews quality issues and adjusts its 

programs and processes to ensure continuous quality improvement.

Cover photographs courtesy of Kittelson & Associates, Inc.
TECHNICAL DOCUMENTATION PAGE 

1. Report No. 

FHWA-HOP-14-034 

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

4. Title and Subtitle 

Incorporating Reliability into the Congestion Management Process: A Primer 

5. Report Date 

August 2014 

6. Performing Organization Code 

7. Author(s) 

Richard G. Dowling, Kamala L. Parks, Brandon Nevers, Jessica Josselyn, 

Steven Gayle (RSG, Inc.) 

8. Performing Organization Report No. 

9. Performing Organization Name and Address 

Kittelson & Associates, Inc. (KAI) 

155 Grand Avenue, Suite 900 

Oakland, CA 94612 

10. Work Unit No. (TRAIS) 

11. Contract or Grant No. 

DTFH61-12-D-00049 

12. Sponsoring Agency Name and Address 

United States Department of Transportation 

Federal Highway Administration 

1200 New Jersey Avenue, SE 

Washington, DC 20590 

13. Type of Report and Period Covered 

September 2013 – August 2014 

14. Sponsoring Agency Code 

HOTM 

15. Supplementary Notes 

The Contracting Officer’s Technical Representative (COTR) was Wayne Berman 

16. Abstract 

This primer explains the value of incorporating travel-time reliability into the Congestion Management Process (CMP) 

and identifies the most current tools available to assist with this effort. It draws from applied research and best practices 

from regional agencies nationwide. It emphasizes the importance of expanding the scope of the CMP to include 

monitoring and addressing non-recurrent congestion utilizing Planning for Operations strategies. It is intended for use 

by state and metropolitan planning organization (MPO) planners as well as operations managers and analysts who are 

planning and programming transportation investments to better manage congestion in our urban areas. 

17. Key Words 

Congestion management process, performance-based planning and 

programming, travel-time reliability, transportation operations, strategic 

Highway Research Program, SHRP 2, planning for operations, 

metropolitan planning, reliability performance measures 

18. Distribution Statement 

No restrictions. 

19. Security Classif. (of this report) 

Unclassified 

20. Security Classif. (of this page) 

Unclassified 

21. No. of Pages 

62 

22. Price 

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

Incorporating Travel-Time Reliability into the Congestion Management 

Process: A Primer

TECHNICAL REPORT DOCUMENTATION PAGE

February 2015
U.S. Department 

of Transportation 

Federal Highway 

Administration 

Dear Colleague, 

AUG 11 2014 

1200 New Jersey Ave., SE 

Washington, D.C. 20590 

In Reply Refer To: 

HOTM-1 

The Federal Highway Administration (FHWA) Office of Operations and the Office of Planning, 

Environment, and Realty are pleased to present this publication titled "Incorporating Travel-Time 

Reliability into the Congestion Management Process (CMP): A Primer". Support for this effort came 

from the second Strategic Highway Research Program (SHRP 2), managed by the Transportation 

Research Board (TRB). Realizing the growing need to address reliability in transportation planning, 

and the importance of the CMP in the metropolitan transportation planning process, the Technical 

Coordinating Committee of SHRP 2 recommended that work be done on incorporating reliability 

into the CMP, utilizing the SHRP 2 Reliability products. 

Reliability is an important element of congestion that historically has not been considered as part of 

the CMP. Across the U.S., congestion due to non-recurring disruptions such as traffic incidents, 

weather, work zones, and special events accounts for an average of 55 percent of total delay. 

Because many of these events are not predictable, they affect the reliability of the system and have a 

significant impact on congestion. The primary objective of this primer is to provide direction and 

potential opportunities for incorporating reliability, specifically travel-time reliability, into the 

CMP and identify the most-current tools available to assist with this effort, including the SHRP 2 

Reliability products. It is intended for use by State and metropolitan planning organization (MPO) 

planners who are involved in the development of the CMP as well as by operations managers and 

analysts who are also engaged in the development of the CMP. This primer explains the value of 

incorporating travel-time reliability into the CMP; how to get started, in a checklist format; and some 

examples, or models, of good practice for incorporating reliability into the CMP. 

Our Offices will be supporting this primer through workshops and related technical assistance 

activities. If you have any comments on this material or need additional copies, please contact 

Jim Hunt at jim.hunt@dot.gov, 717-221-4422; Wayne Berman at Wayne.Berrnan@dot.gov, 

202-366-4069, and/or Egan Smith at Egan.Smith(a),dot.gov, 202-366-6072. 

Jeffrey A. Lindley 

Associate Administrator 

Office of Operations, FHW A 

Sincerely yours, 

Gloria M. Shepherd 

Associate Administrator 

Office of Planning, Environment and Realty, FHW A 
SI* (MODERN METRIC) CONVERSION FACTORS 

APPROXIMATE CONVERSIONS TO SI UNITS

Symbol When You Know Multiply By To Find Symbol 

in inches 25.4 millimeters mm

ft feet 0.305 meters m

yd

mi miles 1.61 kilometers km

yards 0.914 meters m

in2

2 ft square feet 0.093 square meters 2 m

square inches 645.2 square millimeters 2 mm

yd2 square yard 0.836 square meters 2 m

ac acres 0.405 hectares ha 

mi2 square miles 2.59 square kilometers km2

fl oz fluid ounces 29.57 milliliters mL 

gal gallons 3.785 liters L

ft3 cubic feet 0.028 cubic meters 3 m

yd3 cubic yards 0.765 cubic meters 3 m

oz ounces 28.35 grams g

lb pounds 0.454 kilograms kg

T short tons (2000 lb) 0.907 megagrams (or "metric ton") Mg (or "t") 

o

F Fahrenheit 5 (F-32)/9 Celsius oC

or (F-32)/1.8 

fc foot-candles 10.76 lux lx 

fl foot-Lamberts 3.426 2 candela/m cd/m2

lbf 2 lbf/in poundforce per square inch 6.89 kilopascals kPa 

poundforce 4.45 newtons N 

LENGTH

AREA 

VOLUME

3 NOTE: volumes greater than 1000 L shall be shown in m

MASS

TEMPERATURE (exact degrees) 

ILLUMINATION 

FORCE and PRESSURE or STRESS 

APPROXIMATE CONVERSIONS FROM SI UNITS 

Symbol When You Know Multiply By To Find Symbol 

mm millimeters 0.039 inches in

m meters 3.28 feet ft

m

km kilometers 0.621 miles mi

meters 1.09 yards yd

2 mm square millimeters 0.0016 square inches in2

2 m square meters 10.764 square feet ft2

2 m square meters 1.195 square yards yd2

ha hectares 2.47 acres ac

km2 square kilometers 0.386 square miles mi2

mL milliliters 0.034 fluid ounces fl oz 

L liters 0.264 gallons gal 3 m cubic meters 35.314 cubic feet ft3

3 m cubic meters 1.307 cubic yards yd3

g grams 0.035 ounces oz

kg kilograms 2.202 pounds lb

Mg (or "t") megagrams (or "metric ton") 1.103 short tons (2000 lb) T 

o

C Celsius 1.8C+32 Fahrenheit oF

lx lux 0.0929 foot-candles fc 

cd/m2 2 candela/m 0.2919 foot-Lamberts fl

N

kPa kilopascals 0.145 poundforce per square inch 2 lbf/in

newtons 0.225 poundforce lbf

LENGTH

AREA 

VOLUME 

MASS

TEMPERATURE (exact degrees)

ILLUMINATION 

FORCE and PRESSURE or STRESS 

*SI is the symbol for the International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E380.

(Revised March 2003)

Table of Contents

7

Chapter 1 Introduction 13

 

1.1 What is Travel-Time Reliability? 14

1.2 Why Does Reliability Matter Now? 14

1.3 The CMP and the Value of Incorporating Reliability 20

1.4 Purpose of the Primer 23

1.5 Content of the Primer 23

Chapter 2 How to Incorporate Reliability into the

 Congestion Management Process 25

2.1 Objectives and Performance Measures 28

2.2 Diagnosing Causes of Reliability Problems 33

2.3 Generation of Strategies for Addressing Reliability 38

2.4 Evaluation of Strategies 41

2.5 Monitoring Reliability Outcomes 42

Chapter 3 Getting Started 43

3.1 Update Goals, Objectives and Performance Measures 43

3.2 Assess Data Needs and Availability 44

3.3 Diagnose Causes of Unreliability for Select Facilities 44

3.4 Evaluate and Prioritize Reliability Strategies 44

3.5 Prepare CMP Update 45

Chapter 4 Model Congestion Management Plan 47

4.1 One Size Does Not Fit All 47

4.2 Model Plan Excerpts 47

Chapter 5 Summary 55

Chapter 6 References 57

APPENDIX: Congestion Management Process Refresher 59
8

List of Figures

Figure 1. Chart. Causes of Congestion 14

Figure 2. Graph. An Illustrative Example of Typical Travel Time Reporting

 versus What Travelers Experience 15

Figure 3. Chart. 30-Year Growth of Key Metrics in Relation to Highway

 Lane Miles 18

Figure 4. Chart. Typical Capacity and Operations Related Strategies 21

Figure 5. Chart. Highlighted Congestion Management Process Actions for

 Focusing on Incorporating Reliability 26

Figure 6. Graph. A Sample Travel-Time Distribution and Measures

 of Reliability 32

Figure 7. Graph. Dimensions of Reliability with Sample Data 34

Figure 8. Chart. Overview of the Reliability Estimation Methodology from the

 Second Strategic Highway Research Program 37

Figure 9. Chart. Goals, Objectives, and Strategies—An Example 40

Figure 10. Chart. Actions for the Congestion Management Process 60

List of Tables

Table 1. Resources for Incorporating Reliability into the

 Congestion Management Process 27

Table 2. Generic Examples of Reliability Objectives 29

Table 3. Drafting Reliability Objectives 30

Table 4. Reliability Performance Measures for the Congestion

 Management Process 31

Table 5. Example Strategies for Improving Reliability 39

Table 6. Systems Operations Benefits 41

Table 7. Getting Started Checklist 45

Table 8. Example of Resource Requirements for Performance Measures from

 Madison, Wisconsin 49

Table 9. Example of a Performance Monitoring Plan from Madison, Wisconsin 50
List of Acronyms and Symbols

CMP Congestion Management Process (Federal guidelines) or

 Congestion Management Program (locally or regionally adopted)

DOT Department of Transportation

FHWA Federal Highway Administration

GPS Global Positioning System

GIS Geographic Information Systems

HCM Highway Capacity Manual

HOT High Occupancy Toll

HOV High Occupancy Vehicle

ITS Intelligent Transportation Systems

LOS Level of Service

MAP-21 Moving Ahead for Progress in the 21st Century Act

 (Federal surface transportation reauthorization law from

 2012 to the issuance of this report)

MPO Metropolitan Planning Organization

MTP Metropolitan Transportation Plan

NHS National Highway System

NPMRDS National Performance Management Research Data Set

PeMS (California’s) Performance Measurement System

PBPP Performance-Based Planning and Programming

PTI Planning Time Index

SAFETEA- Safe Accountable Flexible Efficient Transportation Equity Act:

LU A Legacy for Users (Federal surface transportation reauthorization

 law from 2005 to 2012)

SHRP 2 The second Strategic Highway Research Program

SOV Single Occupant Vehicle

TIP Transportation Improvement Program

TMA Transportation Management Area

TMC Transportation Management Center

TSM&O Transportation System Management and Operations

TTI Travel Time Index

V/C Volume to Capacity Ratio

VHD Vehicle Hours of Delay

VHT Vehicle Hours Traveled

VMT Vehicle Miles Traveled

9
Photograph courtesy of iStock (Todd Arena)

Overview

Travel-time reliability is an important element of 

congestion that historically has not been considered 

as part of the Congestion Management Process 

(CMP). Taken on average, and as a whole across the 

United States, non-recurring congestion accounts 

for more delay than recurring congestion. Nonrecurring congestion is caused by disruptions, such 

as traffic incidents, weather, road construction and 

maintenance, poor signal timing, and/or special 

events.

Three major factors are driving the focus on traveltime reliability:

Roadway Expansion Constraints – Physical and other 

constraints make traditional capacity improvements 

increasingly difficult. Transportation system 

management and operations strategies (TSM&O), 

designed to address reliability are usually easier to 

implement and can be installed more quickly than 

traditional capacity improvements.

Customer Expectations – The value of travel-time 

reliability is being increasingly recognized as a key 

aspect of transportation performance to system 

users. For personal travel, travel to support commute 

trips, and most importantly travel that affects freight 

operations, research is showing that travel-time 

reliability is valued at a level comparable to, and in 

some cases more than, average travel time.

Federal Surface Transportation Reauthorization 

Law – Moving Ahead for Progress in the 21st Century 

Act (MAP-21) establishes a system reliability goal for 

the national transportation system with an emphasis 

on performance-based planning and programming 

(PBPP) to ensure achievement of that goal. 

U.S. Department of Transportation | Federal Highway Administration

10
11

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer

Overview

This primer identifies opportunities for incorporating 

travel-time reliability into the CMP. It is intended for 

use by state and metropolitan planning organization 

(MPO) planners as well as by operations managers 

and analysts who are planning and programming 

transportation investments to better manage 

congestion in urban areas. The primer illustrates 

how advances in probe data and system detection 

technologies, as well as new analysis tools developed 

under the second Strategic Highway Research 

Program (SHRP 2) [1] program, can enable reliability 

analysis to be incorporated into the CMP.

The primer is organized as follows: 

Chapter 1

Introduction:

Defines travel-time reliability as well as the impetus for 

and value of incorporating it into the CMP.

Chapter 2

How to Incorporate Reliability into the Congestion 

Management Process:

Focuses on key points in the CMP where travel-time 

reliability could be added to create a more robust 

plan. This includes:

• Objectives and performance measures

• Diagnosing causes of reliability problems

• Generation of reliability strategies

• Evaluation of reliability strategies

• Monitoring of reliability outcomes

Many of the data sets and tools for evaluating 

reliability are described in this section, including the 

use products developed as part of SHRP 2.

Chapter 3

Getting Started: 

Provides a checklist for agencies to use for getting 

started on incorporating reliability into their CMP.

Chapter 4

Model Congestion Management Plan:

Demonstrates specific sections of current CMPs in 

which reliability has been incorporated.

Chapter 5

Summary:

Recaps the motivation for the Federal Highway 

Administration (FHWA) to support the development 

of robust CMPs.

Chapter 6

References:

Details the source of materials used for this primer’s 

development.

Appendix

Provides a brief overview of the CMP and reference to 

the Congestion Management Process: A Guidebook

for those who are unfamiliar or need a refresher on the 

process.

11

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer

13

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer

Chapter 1 Introduction

Photograph courtesy of Kittelson & Associates, Inc.

Chapter 1 Introduction

This primer identifies opportunities for incorporating 

travel-time reliability into the Congestion Management 

Process (CMP). It is intended for use by state and 

Metropolitan Planning Organization (MPO) planners as 

well as by operations managers and analysts who are 

planning and programming transportation investments 

to better manage congestion in urban areas.

Travel-time reliability, which considers the effects 

that non-recurring events have on delay over time, is 

an important element of congestion that historically 

has not been considered as part of the CMP. Taken 

on average, and as a whole across the United States, 

non-recurring congestion accounts for more delay 

than recurring congestion. Non-recurring congestion 

is caused by disruptions, such as traffic incidents, 

weather, road construction and maintenance, and/or 

special events, as shown in Figure 1. This is particularly 

true in areas with smaller population sizes that do not 

experience much recurring congestion.

Recurring and Non-Recurring 

Congestion

Recurring congestion, or expected 

congestion, occurs when too many people 

routinely attempt to drive on a roadway 

or enter a transit vehicle at the same time. 

Recurring congestion typically happens 

during commute hours for most regions.

Non-recurring congestion happens when 

there are disruptions to the flow of traffic 

or transit. Disruptions include crashes, 

disabled vehicles, large special events 

(concerts, sports games, etc.), inclement 

weather, and construction work zones. 
U.S. Department of Transportation | Federal Highway Administration

14

Chapter 1 Introduction

Figure 1. Chart. Causes of Congestion

Source: Adapted from Traffic Congestion and Reliability: Trends and Advanced Strategies for Congestion Mitigation, Figure ES.2,

Federal Highway Administration, http://ops.fhwa.dot.gov/congestion_report/executive_summary.htm#what_is_congestion

To date, most CMPs assess congestion using 

traditional proxy measures such as level of service and 

volume-to-capacity ratios. Traffic counts are reduced 

to average annual daily traffic, leading to viewing the 

system on a “typical” day. This approach is attributed 

to the historical costs of continuous data collection 

and to the lack of analysis tools available for assessing 

travel-time reliability.

Advances in probe data and system detection 

technologies have significantly reduced data collection 

costs. Travel times can now be monitored continuously 

and cost effectively at the individual facility and 

network levels, enabling the calculation of reliability. 

Software programs have been developed to translate 

these data directly into performance measures. 

Several research projects on reliability were conducted 

as part of the second Strategic Highway Research 

Program (SHRP 2) [1]. They developed relationships, 

methods, and analytical tools and techniques to 

define, measure, monitor, and improve the reliability of 

roadway networks.

Travel-time reliability is important to the traveling 

public and shippers, and they often factor in how 

predictable their trip time is when making decisions 

about route choice, departure times, or mode of travel. 

Given this importance, along with the advent of data 

sources and analytical tools that make measuring 

and assessing reliability viable, additional guidance is 

needed to enable MPOs to incorporate reliability into 

their planning processes.

1.1 What is Travel-Time

Reliability? 

Travel-time reliability is defined as consistent travel 

times for the same trip as measured day-to-day or 

across different times of the day. If trip times are 

inconsistent, the travel time is considered to be 

unreliable, because it is difficult to generate consistent 

and accurate estimates for it.
15

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer

Chapter 1 Introduction

Travel-time reliability is a metric that is important to 

and innately understood by travelers and shippers. 

Variable or unpredictable travel times make it more 

difficult for travelers and shippers to plan their travel, 

often forcing them to add extra time to protect 

themselves against the uncertainty of arrival times. 

This uncertainty may lead to ineffective or even 

counterproductive travel decisions that waste time 

and money.

Frequent disruptions to normal flows lead to 

uncertainty for the traveling public and freight 

shippers. Figure 2 provides an illustrative example of 

what travelers experience over a year’s time and how 

they are most likely to recall the highest travel-time 

delays. As this figure shows, major delays due to nonrecurring incidents may be infrequent, but their effects 

can be large when they happen. In addition, those 

exceptionally bad days are the ones best remembered 

by the traveling public.

The basic causes of unreliable travel times are (1) an 

imbalance between demand and capacity and (2) the 

congestion that can result from such an imbalance. 

Once congestion occurs, travel times become more 

variable (less reliable and thus less predictable). 

Moreover, congested facilities lack the resilience to 

accommodate unexpected travel interruptions, which 

leads to flow breakdowns and serious degradation of 

reliability. Travel times vary from one day to the next 

because conditions influencing traffic differ each day.

Same Trip

A trip taken on a regular basis with 

identical characteristics, including its 

purpose, origin, destination, time-of-day, 

mode, and route.

How Tr ve

Been Communicated

Annual Average

What Travelers Experience . . .

Travel Times Vary

Greatly Day-to-Day

. . . and what

they remember

Travel

Time

Travel

Time

Jan July Dec Jan July Dec

Figure 2. Graph. An Illustrative Example of Typical Travel Time Reporting versus What Travelers Experience

Source: Travel-Time Reliability: Making it There On Time, All The Time, Federal Highway Administration,

FHWA-HOP-06-070, http://ops.fhwa.dot.gov/publications/tt_reliability/TTR_Report.htm
U.S. Department of Transportation | Federal Highway Administration

16

Chapter 1 Introduction

The SHRP 2 L02 Guidebook [2] identifies seven 

sources of congestion that influence travel-time 

reliability. They are: fluctuations in normal travel, 

inadequate base capacity, special events, traffic 

incidents, weather, traffic-control devices, and work 

zones. Actions responding to these factors fall into 

two broad categories. The first category of actions 

addresses the demand for travel, including the use 

of travel information and pricing and incentivebased strategies to influence when, where, how, 

and how much travel (both personal travel and 

freight movement) occurs. Emerging smart phone 

applications such as for dynamic ridesharing and realtime parking information can also be effective tools 

for managing real-time travel demand. The second 

category of actions includes actions to increase 

roadway capacity or otherwise maximize throughput, 

such as the following:

• Expansions of, or additions to, highway or transit 

facilities;

• Application of better operational and technical 

systems, such as active traffic management and 

intelligent transportation systems, to maximize the 

performance of existing infrastructure;

• Advances in technology and procedures that 

more-quickly restore capacity that has been lost 

as a result of disruptions (incidents, weather 

conditions, work zones); and

• Optimal use of existing transportation system 

capacity controlled by other transportation 

agencies, firms, or individuals. (This can be 

accomplished by providing incentives for mode 

shifts from single-occupant vehicles to multioccupant vehicles and more-effective use of 

alternative rights-of-way).

The types of solutions that can address demand and 

capacity imbalances depend on whether congestion 

can be anticipated or whether congestion results from 

unexpected events. 

When volume routinely approaches or exceeds 

capacity (recurring congestion), demand management 

and capacity increases are likely to be effective in 

improving reliability. In cases in which unexpected 

disruptions cause the bulk of congestion (nonrecurring congestion), techniques that detect 

disruptions and facilitate rapid recovery from those 

events are more likely to be effective. Even for 

situations in which unexpected disruptions cause 

the majority of congestion, however, strategies for 

demand management and capacity increases will 

also warrant consideration. These strategies create 

a capacity margin that helps to ensure the system’s 

resilience in effectively responding to unexpected 

events.

1.2 Why Does Reliability Matter 

Now? 

Traffic congestion due to non-recurring events such 

as traffic incidents, weather, road work zones, and 

special events accounts for a majority of total traffic 

congestion-related delay in the United States. Up until 

recently, there were few options for cost-effectively 

collecting data for non-recurring events, particularly 

unplanned events such as crashes. MPOs and states 

that recognized the importance of travel-time 

reliability early on developed proxy objectives and 

performance measures, such as reducing collisions. 

Most agencies, however, have focused their CMPs on 

recurring congestion.

Why Focus on Reliability Now?

Constraints on expansion of the nation’s 

transportation system, expectations of the 

traveling public, and Federal legislation 

are driving interest in travel-time 

reliability.

Improved monitoring technology and the 

availability of tools through the SHRP 2 

program now make it feasible to evaluate 

reliability.
17

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer

Chapter 1 Introduction

The focus on recurring congestion in CMPs has been 

easier to quantify from a monitoring standpoint, 

but has led to improvement strategies that focus on 

capacity expansion. Capacity expansion is increasingly 

difficult and expensive to implement. Expanding the 

scope of CMPs to address non-recurring congestion 

would mean more data collection and analysis. 

However, it would also lead to an expanded toolbox 

of improvement strategies that would incorporate 

transportation system management and operations 

(TSM&O). TSM&O strategies are generally easier and 

less expensive to implement.

With the growing field of inexpensive travel-time 

monitoring technologies and new prediction tools 

through the SHRP 2 program, it is now feasible to 

develop reliability performance measures. Analysis 

tools have been developed to identify current 

reliability problems and to predict reliability problems 

in the future.

Three major factors have also contributed to driving 

the focus on travel-time reliability by Federal, state, 

and metropolitan planning organizations: constraints 

on further expansion of the nation’s transportation 

system, expectations by the traveling public, and 

recent Federal legislation.

Constraints on Expansion of the

Transportation System 

Photograph courtesy of Kittelson & Associates, Inc.

The era of new roadway construction has largely 

ended in most of the major metropolitan areas of 

the country. In addition, the practice of widening 

existing roadways is also falling out of favor due to 

high costs, the built out nature of many urbanized 

areas, and community desires for more multi-modal 

streets. While vehicle miles traveled (VMT) per-capita 

has been dropping steadily since 2004, population 

growth continues, particularly in urban areas, and this 

has led to more VMT overall. At the same time, transit 

ridership has increased to its highest level since 1956 

[3]. There’s growing momentum for making moreefficient use of the entire existing transportation 

system.

Growth in population, drivers, vehicles, and vehicle 

miles of travel overall has far outpaced roadway 

capacity expansion. As shown in Figure 3, the 

population of the United States increased 36 percent 

in the 30 years between 1980 and 2010, the number 

of auto drivers increased by 45 percent, the number 

of licensed vehicles increased by 50 percent, and the 

annual VMT increased by 94 percent. Meanwhile, new 

lane-miles of highways increased by only 8 percent 

during the same period.
U.S. Department of Transportation | Federal Highway Administration

18

Chapter 1 Introduction

As the physical capacity of our roadways is consumed 

by the growth in traffic, they become more vulnerable 

to disruptions caused by traffic incidents, inclement 

weather, special events, and work zones. These nonrecurring events can occur at any time and place, 

and can cause congestion even in areas that don’t 

usually experience recurring congestion. Variability in 

travel times is increasing on more roadways and for 

more times of the day, in part because non-recurring 

congestion has not typically been addressed in CMPs, 

or in the traditional transportation planning process. 

The highway transportation system has become more 

fragile and more susceptible to major disruptions due 

to traffic incidents.

Vehicle Miles Traveled (VMT) is a 

measurement of miles traveled by vehicles 

in an area over for a specified time 

frame. For example, the Federal Highway 

Administration summarizes monthly and 

yearly VMT for the nation and each state.

Highway Lane Miles is calculated by 

the number of lanes multiplied by the 

length in miles. It can be used to track 

capacity expansion for both existing and 

new roadways.

Figure 3. Chart. 30-Year Growth of Key Metrics in Relation to Highway Lane Miles

Created using data from the United States Census Bureau and the

Federal Highway Administration’s Office of Highway Policy Information, Highway Statistics Series
19

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer

Chapter 1 Introduction

Expectations of the Traveling 

Public

Photograph courtesy of Kittelson & Associates, Inc.

Surveys of the traveling public and freight shippers 

repeatedly show that they value travel-time reliability 

more than speed. They are aware that technologies 

have been developed to extract data from mobile 

devices and to monitor real-time traffic conditions. 

They expect that public agencies will use this data 

to provide real-time information and to alleviate the 

effects of disruptions on the roadway and transit 

network.

Federal Surface Transportation 

Reauthorization Law

On July 6, 2012, President Obama signed into law 

Moving Ahead for Progress in the 21st Century Act 

(MAP-21)[4]. It funds Federal surface transportation 

programs at an average of about $41 billion per fiscal 

year and has been extended through May 31, 2015.

This was the first long-term highway authorization 

enacted since 2005. In addition to funding, MAP-21 

establishes the policy and programmatic framework 

for investments to guide the growth and development 

of nation’s transportation infrastructure. 

MAP-21 established a new paradigm for states and 

MPOs called “performance-based planning and 

programming” (PBPP). This means that MPOs, 

state departments of transportation (DOT), and 

transit operators will be involved in performance 

measurement, target setting, and reporting on the 

outcomes of their transportation investments. MAP21 began this process by setting seven national goals, 

and subsequently prescribing performance measures 

for each. One of the seven goals is: 

“(4) System reliability - To improve the efficiency of 

the surface transportation system.” MPOs that develop 

reliability goals and incorporate reliability into their 

CMPs provide a pathway to developing PBPP elements 

that aid this national goal by improving regional travel.1

Since 1991, Federal transportation law has required 

that MPOs explicitly address congestion. The Safe 

Accountable Flexible Efficient Transportation Equity 

Act: A Legacy for Users (SAFETEA-LU) surface 

transportation reauthorization law stipulated the 

requirement for the use of the CMP in Transportation 

Management Areas (TMAs). This requirement was 

continued under MAP-21. The CMP consists of actions 

employing a variety of performance measures and 

analytic tools to define and identify congestion across 

all modes, and to develop and select appropriate 

strategies to reduce congestion.

1 As of the writing of this primer the notice of proposed rule-making 

(NPRM) had not been released, thus the specific requirements and 

where they will apply were not known.

Photograph courtesy of iStock (B. Esov)
U.S. Department of Transportation | Federal Highway Administration

20

Chapter 1 Introduction

These strategies may include capital projects in 

the metropolitan transportation plan (MTP) and 

transportation improvement program (TIP), or 

operations actions carried out by MPO member 

agencies. While the CMP establishes a set of 

prioritized projects and actions, it does not impose 

upon MPOs a requirement to program them. An 

individual MPO may, for example, assign a low priority 

to congestion mitigation in their planning goals and 

objectives. 

Over time, MPOs will need to pay attention to 

outcomes of the Federal investments in their TIP 

by reporting on performance. Many have only 

rudimentary performance measurement and 

monitoring systems in place. While some of the 

national goals may be limited to the National Highway 

System (NHS), reliability is a system-wide issue for 

most agencies, incorporating freeway, arterial, and 

transit operations.

1.3 The CMP and the Value of

Incorporating Reliability

MPOs, by their very nature, must be responsive to the 

needs of their constituents as they develop plans and 

investment programs for the future of their regions. 

These typically address a wide range of issues, 

including mobility, safety, accessibility for all users, 

and quality of life. Non-recurring congestion can have 

a negative impact on all of these factors. Some MPOs 

are learning to pay more attention to system reliability. 

It is a metric that has become important to their 

constituents and elected officials.

Incorporating travel-time reliability into the CMP 

creates a systematic method to address the issue. 

The benefits include a more-robust understanding 

of the regional transportation system and a toolbox 

of strategies that go beyond capacity expansion 

to include operations and demand management 

solutions. A CMP that does not incorporate reliability 

will be heavily weighted towards traditional capacity 

improvements, missing out on, or under valuing more 

cost-effective operations strategies.

A CMP that adequately incorporates reliability will 

tend to include more (or place a greater weight on) 

operations strategies, such as signal retiming or 

traveler information. Figure 4 demonstrates a variety 

of capacity-related and operations-related strategies 

that may be included in a robust CMP. 

The Value of Reliability

Travel-time reliability is a metric that is 

important to and is innately understood 

by travelers, freight shippers, and elected 

officials.
21

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer

Chapter 1 Introduction

Capacity-Related Operations-Related

Build or Widen 

Roadways

Build or Expand 

Transit Systems

Build or Widen 

Walkways

Increase Transit

Vehicle Fleets

Build or Widen

Bikeways

Arterial

Management

Work Zone

Management

Freeway

Management

Incident

Management

Traveler

Information

Special Event

Management

Travel Weather

Management

Freight

Management

Travel Demand

Management

(TDM)

Transit

Operations and

Management

Figure 4. Chart. Typical Capacity and Operations Related Strategies
U.S. Department of Transportation | Federal Highway Administration

22

Chapter 1 Introduction

Incorporating Travel-Time Reliability Throughout a CMP: An Example from 

the Las Vegas Region

Regional Transportation Commission of Southern Nevada, the MPO for the Las Vegas 

region, has effectively incorporated travel-time reliability performance into its congestion 

management program. To this end, the MPO has developed objectives and performance 

measures, instrumented its network, and developed speed profile curves to assist with 

identifying sources of both recurring and non-recurring congestion. The data sets are 

arranged to be reported in user-defined temporal and spatial groups in order to identify 

reliability issues. Staff at the MPO actively monitors the transportation network and evaluates 

the effectiveness of incident management and ramp metering programs. More information 

can be found at: http://www.rtcsnv.com/planning-engineering/transportation-planning/2013-

2035-regional-transportation-plan-update/

Source: Regional Transportation Commission of Southern Nevada 

Another advantage of incorporating reliability into 

the CMP is that many of the TSM&O strategies for 

addressing reliability problems can be deployed 

more quickly, at lower cost, and with a smaller 

environmental impact than traditional large-scale 

capacity improvements.

Focusing on system management and operations 

has been shown to have positive effects not only 

on reliability, but on safety and the environment as 

well. Many of the steps to create the CMP provide 

opportunities to incorporate travel-time reliability. 

These include:

• Developing goals and objectives

• Identifying performance measures

• Monitoring 

• Identification of problems

• Identification of strategies

• Monitoring effectiveness of implemented 

strategies
23

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer

Chapter 1 Introduction

1.4 Purpose of the Primer 

This primer is intended to provide advice to staff at 

MPOs on how to reevaluate their CMPs. It will show the 

value of integrating travel-time reliability into the CMP 

to address non-recurrent congestion. It will identify 

tools and data sources that are available to assist 

planners in monitoring and predicting travel-time 

reliability. Incorporating reliability in the CMP will result 

in a more-robust regional transportation system with 

objectives, performance measures, and strategies that 

align more closely with public and freight shippers’ 

concerns.

In particular, this primer provides guidance and 

potential opportunities for using products developed 

through the SHRP 2 Reliability focus area. They have 

been developed, in part, to support and advance the 

CMP and Planning for Operations [5] as part of the 

metropolitan transportation planning process. 

SHRP 2 was authorized by Congress to address some 

of the most-pressing needs related to the nation’s 

highway system, including congestion stemming both 

from inadequate physical capacity and from events 

that reduce the effective capacity of a highway facility. 

SHRP 2 reliability products focused on developing 

basic analytical techniques, design procedures, and 

institutional approaches to address the events—such 

as crashes, work zones, special events, and inclement 

weather—that often result in the unpredictable 

congestion that make travel times unreliable. This 

primer also includes guidance for using the National 

Performance Monitoring Research Data Set (NPMRDS) 

and other reliability tools. 

1.5 Content of the Primer 

The primer includes a “How-To” guide for 

incorporating travel-time reliability into an agency’s 

next CMP (Chapter 2). It also contains a guide 

to getting started (Chapter 3) and a model CMP 

(Chapter 4) that use examples from CMPs that have 

incorporated travel-time reliability. The appendix 

contains a CMP refresher (Appendix). 

Throughout the primer are examples from MPOs that 

have included travel-time reliability in their CMPs 

and Planning for Operations processes. The primer’s 

content is sensitive to metropolitan regions of various 

sizes and addresses a range of issues from agencies 

that have very little system performance data to those 

with access to a large amount of data, recognizing 

that the field of transportation data collection 

is resource-intensive but also very dynamic and 

technology-enabled.

Urbanized areas with populations greater than 

200,000 are designated as TMAs by the Federal 

Highway Administration and the Federal Transit 

Administration. MPOs located in long-standing TMAs 

often have many years of experience producing 

congestion management plans. By taking advantage 

of the contents of this primer, MPOs can now include 

non-recurring congestion and travel-time reliability in 

a CMP that provides more value to their constituents.

25

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer

Chapter 2 How to Incorporate Reliability into the Congestion Management Process

Photograph courtesy of iStock (Eugene Gurevich)

Chapter 2 How to Incorporate Reliability into the Congestion

Management Process

This chapter identifies the key points and resources, 

tools, and methods for incorporating reliability into 

the Congestion Management Process (CMP) and 

for supporting Planning for Operations. Those who 

are not familiar with or need a refresher on the CMP 

are directed to the Appendix of this primer. There 

are many resources available to assist agencies 

with developing a CMP that incorporates traveltime reliability. In particular, this chapter shows how 

reliability can be incorporated into the following CMP 

Actions that are shown in Figure 5:

• Develop Regional Objectives

• Develop Multimodal Performance Measures

• Analyze Congestion Problems and Needs

• Identify and Assess Strategies

• Evaluate Strategy Effectiveness 
U.S. Department of Transportation | Federal Highway Administration

26

Chapter 2 How to Incorporate Reliability into the Congestion Management Process

Develop Regional

Objectives

Define CMP Network

Develop Multimodal

Performance Measures

Collect Data/Monitor

System Performance

Analyze Congestion

Problems and Needs

Identify and Assess

Strategies

Program and

Implement Strategies

Evaluate Strategy

Effectiveness

Figure 5. Chart. Highlighted Congestion Management Process Actions for Focusing on Incorporating Reliability

Source: Congestion Management Process: A Guidebook, Figure 2, Federal Highway Administration, FHWA-HEP-11-011.
27

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer

Chapter 2 How to Incorporate Reliability into the Congestion Management Process

Table 1 summarizes the resources referenced in this chapter.

Table 1. Resources for Incorporating Reliability into the Congestion Management Process

The Second Strategic Highway Research 

Program Products

L02 L05 L07 L08 L11 Other

Congestion Management Process

Reliability Monitoring:GuidebookReliability ProjectProgramming GuideDesign for ReliabilityReliability Analysis Toolsfor HCMEvaluating OperationalStrategiesAdvancing MetropolitanPlanning for Operations:Desk ReferencesCongestion ManagementProcess: A GuidebookNational PerformanceManagement Research Data SetOperations Benefit/CostAnalysis Desk Reference

Develop Regional Objectives • • •

Develop Multimodal Performance 

Measures

• •

Analyze Congestion Problems 

and Needs • • • •

Identify and Assess Strategies • • • •

Evaluate Strategy Effectiveness • • • • •
U.S. Department of Transportation | Federal Highway Administration

28

Chapter 2 How to Incorporate Reliability into the Congestion Management Process

2.1 Objectives and Performance

Measures

In order for the CMP to address reliability, it is 

necessary to have stated objectives and performance 

measures for reliability. These objectives and 

performance measures support broad goals that 

are typically established in the metropolitan 

transportation plan (MTP)2 . It is a good idea to review 

and update objectives and performance measures in 

light of new data and tools for predicting the reliability 

of the region’s facilities. CMP updates provide frequent 

opportunities for these reviews.

An additional motivation for ensuring that reliability is 

incorporated into the CMP objectives and performance 

measures is that it establishes a business case for 

dedicating funds to operations strategies through the 

transportation improvement program (TIP).

Objectives and Performance

Measures

Objectives are often tied directly to 

the performance measures chosen. A 

number of sample objectives listed in 

Table 2 utilize the following performance 

measures with which agency staff may be 

unfamiliar:

Travel-time index (TTI) is the total time 

needed for a traveler to arrive on-time for 

a user-defined percent of the time. For 

example, the planning-time index (PTI) 

is a special case of the TTI indicating the 

total time needed for a traveler to ensure 

on-time arrival 95 percent of the time.

Buffer index is the extra time a traveler 

would need to budget compared to the 

average travel time to ensure on-time 

arrival 95 percent of the time.

2 MPO practitioners tend to refer to their MTP as their long-range 

transportation plan (LRTP)
29

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer

Chapter 2 How to Incorporate Reliability into the Congestion Management Process

Setting Reliability Objectives

The Federal Highway Administration (FHWA) report, 

Advancing Metropolitan Planning for Operations:

The Building Blocks of a Model Transportation Plan 

Incorporating Operations [6] found at http://ops.fhwa.

dot.gov/travel/plan2op.htm, provides the wording for 

several example objectives that relate to reliability 

performance measures.

Generic examples shown in Table 2 serve as a starting 

point for agencies seeking to establish reliability 

objectives. The examples include objectives for 

reducing non-recurring delay, the buffer index, the 

planning time index (PTI), travel time, and variability. 

There is also a sample objective for improving transit 

on-time performance.

Table 2. Generic Examples of Reliability Objectives

Category Operations Objective

Non-Recurring Delay Reduce total person hours of delay (or travel-time delay per capita) by time period 

(peak, off-peak) caused by:

(Option 1) scheduled events, work zones, or system maintenance by X hours in Y years. 

(Option 2) unscheduled disruptions to travel by X hours in Y years. 

(Option 3) all transient events such as traffic incidents, special events, and work zones 

by X hours in Y years.

Buffer Index Decrease the buffer index for (specific travel routes) by X percent over the next Y years.

Decrease the average buffer index for (multiple routes or trips) by X percent over Y 

years.

Reduce the average buffer time needed to arrive on-time for 95 percent of trips on 

(specified routes) by X minutes over Y years.

Planning Time Index Reduce the average planning time index for (specific routes in region) by X (no units) 

over the next Y years.

Reduce the average planning time for (specific routes in region) by X minutes over the 

next Y years.

Travel Time Reduce the average of the 90th (or 95th) percentile travel times for (a group of specific 

travel routes or trips in the region) by X minutes in Y years.

Reduce the 90th (or 95th) percentile travel time for each route selected by X percent 

over Y years.

Variability Reduce the variability of travel time on specified routes by X percent during peak and 

off-peak periods by year Y.

Transit On-Time Performance Improve average on-time performance for specified transit routes/facilities by X percent 

within Y years.

Source: Adapted from Advancing Metropolitan Planning for Operations: The Building Blocks of a Model Transportation Plan Incorporating 

Operations – A Desk Reference, Reference Tables 3.2.2, Federal Highway Administration, FHWA-HOP-10-027.
U.S. Department of Transportation | Federal Highway Administration

30

Chapter 2 How to Incorporate Reliability into the Congestion Management Process

Another good source of information on the 

development of reliability objectives and 

performance measures is the SHRP 2 L05 report, 

Incorporating Reliability Performance Measures 

into the Transportation Planning and Programming 

Processes: A Guide [7], available at http://www.

trb.org/Main/Blurbs/168855.aspx. As stated in the 

L05 guide, it is important to examine the current 

reliability performance of the system when setting 

MTP goals and CMP objectives. This is to ensure that 

the goals and objectives relate to the fundamental 

issues faced by the agency and are meaningful to 

the agency. Because MTP goals and CMP objectives 

are set through a collaborative process that 

includes stakeholders, it is important to provide the 

stakeholders with information on reliability to help 

facilitate these discussions. The L05 guide goes 

into more detail about the kind of data and types of 

information that will be useful in establishing agency 

reliability objectives, as shown in Table 3. 

Setting Goals and Objectives

Goals for reliability are typically 

developed as part of the Metropolitan 

Transportation Plan. They are often 

broadly worded, such as “Improve System 

Reliability.”

Objectives can be developed in more 

detail to support the region’s reliability 

goals as part of the CMP.

Agencies should examine the current 

reliability performance of their system 

before adopting goals and objectives 

through a public process.

Table 3. Drafting Reliability Objectives

Improve Reliability

. . . On . . . . . . In . . . . . . For . . . . . . By . . .

...Interstates...

...arterials...

...National Highway System...

...key corridors...

...key routes or corridors...

...urban areas...

...rural areas...

...key subareas...

...Freight...

...Transit...

...Commuters...

...Visitors...

...improving incident management.

...improving storm management.

...improving safety.

...improving work zone management.

...managing demand.

...improving special event management.

...improving traffic operations.

Source: Incorporating Reliability Performance Measures into the Transportation Planning and Programming Processes: A Guide,

SHRP 2 L05 report, Table 3-1, Transportation Research Board, Washington, DC, 2013.
31

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer

Chapter 2 How to Incorporate Reliability into the Congestion Management Process

Selecting Reliability Performance 

Measures

Travel-time reliability can be measured in several ways. 

The task is to take the entire distribution of travel 

times over the course of a year and represent it by a 

few numerical indices that can be used to measure 

progress towards the CMP objectives for reliability.

The recently adopted Chapter 36 (Volume 4) of the 

Highway Capacity Manual (HCM) [8] identifies several 

candidate performance measures. The ones most 

applicable to the CMP are defined in Table 4.

Figure 6 illustrates these measures using a sample of 

a travel-time distribution for an entire year (excluding 

weekends and holidays and non-peak hours). 

The Planning Time Index (PTI)

The PTI is identified in the Highway 

Capacity Manual as one of the most 

intuitive and consistent measures for 

reliability. A PTI of 1.5, for example, means 

that a traveler should plan on 50 percent 

more time for their trip compared to 

light traffic conditions for a 95 percent 

probability of arriving on time.

Table 4. Reliability Performance Measures for the Congestion Management Process

Reliability Measure Definition

85th Percentile Travel Time Index 

(TTI)

The ratio of the 85th-percentile highest vehicle-hours traveled (VHT) on the CMP 

system divided by the VHT that would have been expended if the same trips could have 

been completed at their free-flow speed. (unitless)

Planning Time Index 95th Percentile TTI. The ratio of the 95th-percentile highest vehicle-hours traveled 

(VHT) on the CMP system divided by the VHT that would have been expended if the 

same trips could have been completed at their free-flow speed. (unitless)

Reliability Rating Percentage of trips experiencing TTI less than 1.33 for freeways or 2.50 for urban 

streets. (These thresholds are generally at the speed where level of service (LOS) 

deteriorates from LOS “E” uncongested to LOS “F” congested). (unitless)

Failure Measure Similar to Reliability Rating, but using agency-set minimum acceptable threshold 

speeds for the facilities rather than those specified by the HCM and its definition of 

levels of service. (unitless)

Note: Percentile TTI is the ranking from lowest to highest of a collection of travel time indices measured over the course of a year.

The 95th percentile highest TTI, is the value that 95 percent of the observations fall below.
U.S. Department of Transportation | Federal Highway Administration

32

Chapter 2 How to Incorporate Reliability into the Congestion Management Process

Figure 6. Graph. A Sample Travel-Time Distribution and Measures of Reliability

Source: Adapted from Incorporating Reliability Performance Measures into the Transportation Planning and Programming Process: A Guide, 

Figure 2-1, SHRP 2 Report L05, Transportation Research Board, Washington, DC, 2013

Local Resources for Objectives and 

Performance Measures

The agency might consider drawing on the following 

resources and stakeholders in developing its reliability 

objectives, identifying performance measures, and 

seeking data on reliability.

• General public

• State departments of transportation

• Local and metropolitan transit agencies

• City and county public works departments 

• Local traffic signal operators and technicians

• Local and state public safety agencies (police, fire, 

and emergency responders)

• Major employers and universities

• Major venue operators

• Freight and delivery companies

• Local weather experts

• Local and metropolitan tolling authorities
33

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer

Chapter 2 How to Incorporate Reliability into the Congestion Management Process

2.2 Diagnosing Causes of 

Reliability Problems

Once an agency has committed to establishing 

reliability goals, objectives, and performance 

measures, the next steps are to identify the existing 

reliability problems and to diagnose their causes. As 

described earlier, this analysis can provide important 

input to stakeholders for the development of goals, 

objectives, and performance measures.

Identifying Existing Reliability 

Problems

To identify existing reliability problems, the analyst 

must do the following:

• Choose the facilities and study periods for the 

reliability analysis;

• Collect data for reliability analyses;

• Estimate reliability from other data sources 

when direct measurements of reliability are not 

available; and 

• Investigate and diagnose the causes of reliability 

problems.

Choosing Facilities and Study Periods for Reliability 

Analysis

Reliability analyses require more staff resources, more 

analysis resources, and more data sources than typical 

planning or operations analysis studies (although, 

much of this extra information can be handled with 

default inputs, as explained later). Consequently, it is 

wise to spend some time thinking through the exact 

focus of the reliability analysis.

There is little to be gained by expending analysis 

resources on lightly traveled times of day, days of year, 

and lightly traveled facilities. Also, including times of 

day and days of year for a facility when there are likely 

to be few reliability problems will tend to “wash out” 

the results, hiding peak-period reliability problems 

behind an excess of light off-peak traffic conditions.

Diagnosing Causes of Reliability 

Problems

SHRP 2 L02 – Establishing Monitoring 

Programs for Travel Time Reliability: A 

Guidebook [2] is a useful resource for 

understanding the different causes of 

congestion.

If lightly-traveled days are to be included then the 

analyst will want to consider whether the reliability 

results should be weighted according to the amount 

of travel each day.

There is currently no explicit requirement that 

reliability analysis be applied to all of the facilities and 

modes in the CMP. Consequently, it is wise for the 

analyst to expend his or her resources on evaluating 

those facilities, days of the week, and times of the 

day where reliability is likely to be a significant issue. 

Agencies that have invested significant resources 

into travel-time reliability, such as the Regional 

Transportation Commission of Southern Nevada, 

divide the year into seasons that reflect normal 

changes in travel demand for conducting historical 

analysis.

Reliability analysis is a three-dimensional analysis, 

expanding the typical single representative day 

analysis of a CMP to the entire year. The analyst must, 

therefore, specify the focus and limits of the reliability 

analysis both in terms of the typical CMP (peakperiod, major facilities) and in terms of the days of the 

year covered by the analysis.
U.S. Department of Transportation | Federal Highway Administration

34

Chapter 2 How to Incorporate Reliability into the Congestion Management Process

Figure 7 shows the typical dimensions of time, space, 

and days-of-the-year involved in a reliability analysis. 

The example shown here is for a single direction of 

a freeway (the horizontal axis of this figure). The 

horizontal axis represents distance along the freeway 

from upstream to downstream. The vertical axis 

shows the time dimension. In this example, it is the 

3-hour weekday PM peak-period extending from 3 

PM to 6 PM. These first two dimensions are covered 

by a typical, conventional CMP analysis. The “z-axis” 

(the diagonal direction in the chart indicating depth) 

represents the number of weekdays in the year 

(excluding holidays) for which the reliability analysis 

will be performed. The m atrices (composed of green, 

yellow and red cells within each matrix) represent 

the snapshot of congestion on the freeway each day. 

These matrices show when and where congestion 

starts each day, how far up the freeway the queuing 

extends (the red areas in the matrices), and when the 

congestion dissipates.

Regarding the selection of facilities for inclusion in the 

reliability analysis, the significance of the reliability 

problem on a facility will vary according to the goals, 

objectives, and sensitivities of the region. Generally, 

if a facility does not regularly experience recurring 

peak-period congestion (whether on the weekdays 

or weekends and holidays), reliability is unlikely to be 

a significant problem from the perspective of most 

public agencies. However, exceptionally frequent 

crashes, incidents, special events, work zones, and 

weather-related blockages may cause reliability to be 

a significant problem from the point of view of the 

agency and local residents, regardless of the lack of 

recurring peak-period congestion.

Figure 7. Graph. Dimensions of Reliability with Sample Data

Source: Highway Capacity Manual, Chapter 37 – Travel Time Reliability: Supplemental, Exhibit 37-21,

Transportation Research Board, Washington, DC, 2012
35

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer

Chapter 2 How to Incorporate Reliability into the Congestion Management Process

How To Get Reliability Data

The National Performance Management Research 

Data Set (NPMRDS) is a travel-time data set for the 

National Highway System (NHS)—available to MPOs 

and state DOTs through FHWA—that can be used 

for reliability analyses. Agencies may also seek the 

data from commercial providers or from local traffic 

management centers (TMCs).

The National Performance Management Research

Data Set (NPMRDS)

The NPMRDS contains five-minute average travel 

times for trucks (FHWA vehicle classes 7 and 8 only) 

and other motorized vehicles on the NHS (generally 

Interstate and the national aid highway system).3 The 

travel times are for traffic message channel segments, 

as defined by the private sector for providing driving 

instructions to the general public using Global 

Positioning Systems (GPS).4

Historical data is available starting from October 2011 

for the Interstate and starting from July 2013 for all 

other roads on the NHS. The datasets are large and 

require some experience working with exceptionally 

large databases and Geographic Information Systems 

(GIS).

The NPMRDS is made available to state DOTs and 

MPOs to use for their performance management 

activities through a license acquired by FHWA. 

Updates to the data set are made available monthly 

(for the prior month). To request permission to access 

the data set, send an e-mail to Heretraffic.nhsdata@

here.com. For more information go to: http://www.ops.

fhwa.dot.gov/perf_measurement/index.htm

3 Note that MAP-21 added principal arterials to the NHS.

4 A traffic message channel segment ends when the guidance device 

must tell the driver to turn at the intersection or ramp gore point, 

when speeds change, or at state boundaries.

Monitoring and Identification of 

Causes of Congestion

California DOT (Caltrans) has invested 

heavily in measuring travel-time reliability 

and developing programs that improve 

operations, particularly in the San 

Diego region (District 11). The statewide 

Performance Measurement System (PeMS) 

is a web-based software system that 

collects data from over 30,000 detectors 

on the highway system every 30 seconds 

and automatically processes and stores 

the data. Data from other sources, such as 

the California Highway Patrol’s Computer 

Aided Dispatch system, are fed into PeMS 

in real-time or as archived information. 

District 11 has taken this system further 

by incorporating an Arterial Performance 

Measurement System (A-PeMS) and a 

Transit Performance Measurement System 

(T-PeMS). More details can be found at 

http://pems.dot.ca.gov/.

Other Reliability Data Sources

There are also several other public and private sector 

sources of travel-time reliability data. The local TMC 

may be a good source of archived travel-time data 

for freeways in the urban area. Ideally, the travel-time 

data is obtained from timing the movement of vehicles 

along the facility. This is usually done by tracking GPSequipped cell phones, Bluetooth devices, or toll-tags 

in the vehicles. Travel times may also be inferred from 

loop detector or video detector spot speeds. However, 

these estimates of travel times from spot-speed 

measurements will not be as good as direct point-topoint measurements of travel time.
U.S. Department of Transportation | Federal Highway Administration

36

Chapter 2 How to Incorporate Reliability into the Congestion Management Process

Gathering Reliability Data

Generally, a minimum of one-year of travel-time 

data is needed to measure reliability. Other data, 

such as incident logs, weather conditions, road work 

logs, and 24/7 traffic counts for the same period 

are needed for determining what proportion of the 

reliability problems are related to incidents, weather, 

construction, and demand.

Estimating Reliability When Data 

Are Not Available 

Various recently developed methods are available 

for estimating reliability when direct measurements 

of travel-time are not available (or where it is desired 

to predict future reliability under different future 

scenarios). These methods range from relatively 

quick planning methods requiring little data to moreelaborate operations analysis methods that enable 

the agency to test the reliability impacts of different 

advanced traffic operations improvements. These 

methods are briefly described below with references 

to where readers can go to get more information and 

to acquire the computational tools needed to employ 

them.

The SHRP 2 L07 (Design Guide) Reliability Models

The SHRP 2 L07 project, Identification and Evaluation 

of Cost-Effectiveness of Highway Design Features 

to Reduce Nonrecurrent Congestion [9], developed 

a spreadsheet tool to predict travel-time reliability 

distributions. The L07 reliability estimation model 

employs four variables to estimate the cumulative 

percentile travel-time indices for demand/capacity 

ratios less than or equal to 80 percent.

The L07 model requires the following inputs:

• The average annual demand/capacity ratio.

• Annual lane-hours lost due to incidents and work 

zones (a procedure is provided in the spreadsheet 

for estimating this input as a function of the hours 

of rainfall per year, and the hours of snowfall per 

year).

For more information on SHRP 2 L07 and 

the spreadsheet tools, go to the SHRP 2 

research website at: http://www.trb.org/

StrategicHighwayResearchProgram2SHRP2/

reliabilityinplanning.aspx

The SHRP 2 L08 (Highway Capacity Manual)

Reliability Models

The SHRP 2 L08 project [10] developed a method 

for estimating travel-time reliability that employs the 

Highway Capacity Manual (HCM). As such, the SHRP 

2 L08 methodology, as documented in draft chapters 

36 and 37 of the HCM, is a macroscopic, operations 

analysis-level approach to estimating reliability. 

Two methodologies were developed, one for 

freeway facilities, the other for arterial streets. Both 

methodologies involve the generation of different 

demand, weather, and incident scenarios, and then 

the application of the core HCM analysis methodology 

specific to each facility (freeway or urban street) to 

each scenario, as shown in Figure 8.

Both methodologies require HCM operations analysislevel geometric, control, and demand inputs for 

the study facility. Like in the original HCM methods, 

defaults can be used for many of the required HCM 

analysis inputs.

Data on demand variability is required, and both 

methodologies provide default demand variability 

factors. However, given the variation in demand 

variability between facilities in the same metropolitan 

area, it is recommended that local site-specific data 

on demand variability be used whenever feasible. The 

freeway methodology includes two sets of default 

demand variability factors, one for urban freeways, the 

other for rural freeways.

Data on weather events of the year are required. 

However, airport weather data for most major urban 

areas of the U.S. are included in both of the SHRP 

2 L08 spreadsheets. The freeway methodology 

provides default weather event probabilities for 101 

metropolitan areas of the United States. 

Facility-specific incident data are best, but can be 

estimated from crash data for the facility. 
37

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer

Chapter 2 How to Incorporate Reliability into the Congestion Management Process

Figure 8. Chart. Overview of the Reliability Estimation Methodology from the

Second Strategic Highway Research Program

Source: Incorporation of Travel Time Reliability into the HCM, draft final report for SHRP 2 Report L08,

Exhibit 36-1, Transportation Research Board, Washington, DC, 2012

At a minimum, data on crash rates for the facility are 

required by both methodologies. Both methodologies 

provide lookup tables of factors for expanding crashes 

to lane-closure incidents by severity and duration.

For more information on SHRP 2 L08 and 

the spreadsheet tools, go to the SHRP 2 

research website at: http://www.trb.org/

StrategicHighwayResearchProgram2SHRP2/

reliabilityinplanning.aspx

Diagnosing the Causes of 

Unreliability 

If data for calculating reliability are available from 

NPMRDS or other travel-time archives of this type, 

then the procedures provided in SHRP 2 Project L02 

[2] can be used for diagnosing the causes of reliability 

problems. The travel times measured in the field are 

grouped by segment and five-minute time period. 

The time periods are then designated “congested” or 

“uncongested” based on the observed travel times. 

For each congested five-minute time period, the 

analyst scans logbooks of weather, work zones, 

crashes, and other incidents to assign a “cause” for the 

congestion. The last cause considered is “demand.” 

That cause is assigned to the five-minute time period 

only if no other cause has already been assigned to 

the congested time period and if the demand is two or 

more standard deviations above the mean. The analyst 

then sums up the vehicle-hours traveled (VHT) or 

vehicle-hours of delay (VHD) for each five-minute time 

period and segment and tallies the results by cause. 

Additional details are provided in the SHRP 2 L02 

Guidebook [10], available at:

http://www.trb.org/

StrategicHighwayResearchProgram2SHRP2/

DataandAnalysisfor.aspx

If reliability is estimated (because data is not 

available), the tools used to estimate reliability will 

provide information for assessing the causes of 

unreliability. The specifics vary with the tool selected. 

Some tools generate results automatically while others 

require the user to examine the calculations and 

separately compute the additional desired information.
U.S. Department of Transportation | Federal Highway Administration

38

Chapter 2 How to Incorporate Reliability into the Congestion Management Process

2.3 Generation of Strategies for

Addressing Reliability

Strategies should directly correlate to the identified 

needs regarding reliability, but they should also 

link back to earlier actions in the CMP such as the 

objectives and overall goals the region is trying to 

achieve with respect to reliability. The performance 

measures identified should be used as the means to 

determine how well strategies perform in addressing 

the region’s goals and objectives. As congestion 

can come in two forms—both recurring and nonrecurring—identification of needs and relevant 

strategies should be developed under both conditions. 

Typical strategies for addressing reliability are shown 

in Table 5.

Reliability improvement strategies should be 

developed in coordination and collaboration with 

other government partners to maximize opportunities 

for consideration. It is valuable to include people with 

day-to-day operations planning knowledge, and others 

responsible for implementing operations strategies in 

a region.

Resources

For help with identifying strategies and 

treatments to address specific reliability 

problems, the following are useful 

resources: 

• SHRP 2 L05 - Incorporating 

Reliability Performance Measures 

into the Transportation Planning and 

Programming Process: A Guide [7]

• SHRP 2 L11 - Evaluating Alternative 

Operations Strategies to Improve 

Travel Time Reliability: Final Report

[11]

Objectives to improve travel-time reliability may include strategies such as dynamic messaging signs.

Photograph courtesy of Kittelson & Associates, Inc.
39

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer

Chapter 2 How to Incorporate Reliability into the Congestion Management Process

Table 5. Example Strategies for Improving Reliability

Reliability Strategy Areas Reliability Strategies

Demand Management Measures • Programs that encourage transit use, ridesharing, telecommuting, and flexible work 

schedules

• Guaranteed ride home

• Car sharing and bike sharing

• Pedestrian and bikeway improvements

• Roadway congestion pricing

• Parking management and pricing

• Freight rail and port improvements to reduce truck travel on highways

• Growth management (mixed use, higher intensity developments)

Operational Improvements • Metering, reversible lanes, access management, temporary shoulder use

• Signal optimization, geometric improvements, transit signal priority, traffic calming

• Traffic incident management (more patrol cars, protocol for directing traffic, 

pullout areas)

• Work zone rules (lane closures occur during periods of least demand, minimize the 

number of lane closures, provide walking and biking access where feasible)

• Special event traffic plans

• Snow or debris removal plans (response times, ensure clearance of roadways, 

bikeways and sidewalks, appropriately-sized equipment)

• Traveler information

• Freight management, including delivery window restrictions

• Detection 

• Cameras

• Changeable message signs

• Active traffic management

Public Transportation 

Improvements

• More frequent service to address crowding

• Service expansion in congested areas

• Operational improvements (transit signal priority, bus bulb-outs, queue jump lanes)

• Bus stop consolidation

• Operational control strategies (i.e., changes to normal route operation in response 

to delay-causing events)

• Fleet maintenance strategies (e.g., preventative maintenance, vehicle replacement)

Road Capacity Improvements • New HOV/HOT lanes

• New mixed flow lanes

• Intersection widening

• Interchange reconfiguration

• Truck climbing lanes

• Freeway widening at bottlenecks

Source: Adapted from Congestion Management Process: A Guidebook, Federal Highway Administration, FHWA-HEP-11-011.
U.S. Department of Transportation | Federal Highway Administration

40

Chapter 2 How to Incorporate Reliability into the Congestion Management Process

Figure 9 illustrates the desired linkages between goals, 

objectives, and strategies for one example objective 

and a few example strategies. This figure shows how 

the single goal of improving system reliability can 

be tied to the objective of reducing non-recurring 

delay (one of several possible objectives that could 

be tied to the goal of improving system reliability). 

This single objective is then broken down into two 

more specific objectives: reducing scheduled delay 

(such as delay due to work zones and special events) 

and unscheduled delay (such as delay due to traffic 

incidents and emergency maintenance). Scheduled 

delay is then reduced by considering strategies such 

as improving work-zone management, and improving 

special-event management. 

Unscheduled delay is addressed with strategies 

that improve incident management, weather travel 

management, and emergency management. Figure 9

also demonstrates, as an example, specific strategies 

that could be implemented to improve traffic incident 

management. Such strategies demonstrated here 

include reducing time for posting traveler alerts, 

increasing coverage by incident response teams, 

and increasing the number of traffic signals with 

emergency pre-emption. Agencies can employ a 

similar process to identify appropriate strategies for 

improving travel weather management and improving 

emergency management.

Improved System

Reliability

Reduce Non-Recurring

Delay Per Person

Reduce Scheduled Non-Recurring

Delay Per Person

Improve Work

Zone Management

Improve Transport

Incident Mangement

Reduce Unscheduled Non-Recurring

Delay Per Person

Improve Special

Event Management

Improve Travel

Weather 

Management

Improve Emergency 

Management

Reduce Time to Post Traveler Alert 

on Dynamic Message Signs

Organize Additional Regional Coordinated

Incident Response Teams

Increase Number of Corridors 

Covered by Incident

Response Teams

Increase Number of Traffic Signals 

with Transit Priority and

Emergency Pre-empt

Strategies Objectives Goals

Figure 9. Chart. Goals, Objectives, and Strategies—An Example

Source: Adapted from Advancing Metropolitan Planning for Operations: The Building Blocks of a Model Transportation Plan

Incorporating Operations - A Desk Reference, Figure 2, Federal Highway Administration, FHWA-HOP-10-027.
41

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer

Chapter 2 How to Incorporate Reliability into the Congestion Management Process

2.4 Evaluation of Strategies

An evaluation is conducted to estimate the expected 

benefits of the strategies in comparison to their 

expected capital and operating cost requirements. The 

analysis may be quantitative or qualitative depending 

on the nature of the strategies and the resources 

available to the agency. Similar to the strategies, 

the evaluation criteria used in the analysis should 

directly link to the MTP goals and CMP objectives, 

CMP network, and multimodal performance measures. 

Strategies that move forward into funded plans should 

indicate strong performance through an objectivesdriven, performance-based approach. In addition to 

travel-time reliability performance, the evaluation 

will involve identifying the range of capital, staffing, 

technology, training, and maintenance requirements of 

operations deployments. Table 6 presents the general 

range of benefits and cost-benefit ratios that can be 

expected for typical operations strategies.

As different sources of congestion typically affect a 

metropolitan region, the analysis should review major 

recurring and non-recurring congestion problems 

(demand fluctuations, bottlenecks, peaking, incidents, 

weather, safety, construction, special events, etc.) 

and match problems to functional (work, recreation, 

freight), regional (urban and rural), corridor 

(thoroughfare, interstate), and network (freeways, 

arterials, transit) intensity and significance.

Methods for forecasting the reliability effects of 

different improvement strategies—including SHRP 

2 tools L07 and L08—are described in Section 2.2 , 

“How to Get Reliability Data,” in the subsection on 

“Estimating Reliability When Data Are Not Available.”

Table 6. Systems Operations Benefits

Strategy Benefits and

Benefit-Cost Ratios Safety Impact Mobility Impact Energy/Environmental Impact

Traffic incident management

• Safety service patrols

• Surveillance and detection

Incident duration reduced

30-50 percent

2:1 to 42:1

8:1

High

High

High

High

High

High

High

High

High

Road weather information systems 2:1 to 10:1; crash rates reduced 

7 to 80 percent High High High

Traveler information dynamic 

message signs

3 percent decrease in crashes; 

5 to 15 percent improvement in 

on-time performance

Low High Low

Work zone management 2:1 to 40:1; system delays 

reduced up to 50 percent High Medium Medium

Active traffic management Throughput increased by 3 to 7 

percent; decrease of incidents 

of 3 to 30 percent

High High Medium

Source: Adapted from: U.S. Department of Transportation, Intelligent Transportation Systems Joint Program Office, 2009.

For more information and for additional strategies see http://www.plan4operations.dot.gov/topsbctool/index.htm.
U.S. Department of Transportation | Federal Highway Administration

42

Chapter 2 How to Incorporate Reliability into the Congestion Management Process

2.5 Monitoring Reliability 

Outcomes

Once an agency has incorporated reliability into 

the CMP, the next (and last) step is to monitor the 

outcomes of the improvements and strategies put into 

place by the CMP. Section 2.2 describes data sources 

and estimation methods for monitoring reliability. 

See FHWA’s Use of Archived Operations Data in 

Transportation Planning [12] for examples of current 

practice employing archived traffic operations data in 

planning analyses.

The monitoring cycle (the number of months or 

years between reviews of the system reliability) is 

determined by the agency. This cycle might coincide 

with the CMP update cycle. The frequency of 

monitoring depends on agency staff resources. The 

NPMRDS enables the agency to choose monitoring 

cycles as frequently as once a month.

Because the CMP is an iterative process, it is 

dynamic and expected to be responsive to actual 

system performance. Strategies and actions that 

performed as expected, with positive benefit, may 

be retained in subsequent CMPs, while those that 

underperformed would be considered for elimination. 

Care must be given to fully understand how much of 

the performance outcome is attributable to the CMP 

strategy, and how much is attributed to changes in 

background conditions.
43

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer

Chapter 3 Getting Started

Photograph courtesy of Kittelson & Associates, Inc.

Chapter 3 Getting Started

This chapter provides a checklist for agencies to use 

to get started on incorporating reliability into their 

Congestion Management Process (CMP).

3.1 Update Goals, Objectives and

Performance Measures

1. Assess current goals, objectives, and performance 

measures.

a. Ensure alignment with The Moving Ahead for 

Progress in the 21st Century Act (MAP-21) 

performance rule for reliability.5

2. Work with stakeholders to develop reliability 

goals, objectives, and performance measures (see 

Section 2.1).

a. Develop business case(s) for including 

reliability in the CMP as well as the 

metropolitan transportation plan (MTP).

b. Conduct a pilot analysis of a prominent 

facility to test various reliability metrics and 

determine which metrics are most applicable 

and to educate stakeholders on how reliability 

can be applied.

Integrating Reliability into the 

Metropolitan Transportation Plan

SHRP 2 L05 - Incorporating Reliability 

Performance Measures into the 

Transportation Planning and Programming 

Process: A Guide [7] is a useful resource 

for integrating reliability into both the 

MTP and CMP.

c. Review proposed changes with stakeholders.

3. Refine goals, objectives and performance 

measures to incorporate reliability based on 

stakeholder feedback.

5 Rule-making at the national level had not been released as of the 

date of this publication. 
U.S. Department of Transportation | Federal Highway Administration

44

Chapter 3 Getting Started

3.2 Assess Data Needs and

Availability

1. Review current data collection program against 

recommendations in Section 2.2. If satisfactory, 

skip remaining sub steps and proceed to Step 3.3.

2. Check with local and national data sources to 

obtain one year of travel-time data along with 

corresponding incident logs, traffic counts, and 

other event conditions such as weather and 

construction.

a. The National Performance Management 

Research Data Set (NPMRDS) contains 

5-minute travel-time data for freeways going 

back go October 2011 and for NHS roadways 

going back to July 2013.

b. Transportation management centers 

(TMC) may have archived data for select 

facilities from system detectors, toll tag 

readers, Bluetooth readers, or other probe 

measurements.

c. Private vendors: check to see if your state 

department of transportation (DOT) has 

purchased 3rd party travel-time data.

3. If data are not available, refer to the second 

Strategic Highway Research Program (SHRP 2) 

resources for estimating reliability using predictive 

tools.

3.3 Diagnose Causes of

Unreliability for Select

Facilities

1. Review current methods for identifying and 

diagnosing the causes of reliability problems 

against recommendations in Section 2.2. If 

satisfactory, skip remaining sub steps and proceed 

to Step 3.4.

2. Select facilities for analysis that are prone to 

reliability impacts, including: 

a. Highly congested facilities;

b. Major freight routes;

c. Corridors of major significance (bridges, 

tunnels, etc.);

d. Routes that serve high volumes of seasonal 

recreational traffic;

e. Routes subject to inclement weather (snow, 

ice, and visibility);

f. Routes that receive complaints by system 

users; and

g. Routes in metropolitan areas designated 

under the Real-Time System Management 

Information Program (see http://www.ops.

fhwa.dot.gov/1201/)

3. Select time of day (morning or evening peakperiod) and days of year for reliability analysis.

4. Calculate reliability performance measures 

identified in 3.1.3 for facilities selected in 3.3.2.

5. Diagnose causes of unreliability following 

recommendations in Section 2.2:

a. Demand fluctuation;

b. Incidents;

c. Weather;

d. Special Event; and

e. Construction.

3.4 Evaluate and Prioritize

Reliability Strategies

1. Compare current method for identifying, 

evaluating, and prioritizing reliability improvement 

strategies against guidance in Sections 2.3 and 

2.4. If satisfactory, skip remaining sub steps and 

proceed to Step 5.

2. Identify strategies to address causes of 

unreliability (see Tables 4 and 5).

3. Assess benefits, costs, and level of impact (see 

Table 6).

4. Set targets consistent with MAP-21.
45

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer

Chapter 3 Getting Started

3.5 Prepare CMP Update

1. Option 1: Annual Update

a. An annual update is not required, but may be 

desirable because it provides an opportunity 

to the metropolitan planning organization 

(MPO) to assess progress on achieving its 

targets. The performance of various strategies 

and actions that have been implemented 

is assessed for effectiveness. The CMP may 

be modified to focus on the most-effective 

strategies. 

b. Assess if the CMP is integrated into the MTP.

2. Option 2: Major Update

a. A major update should be considered after 

adoption of the MTP (every 4 or 5 years 

depending on air quality attainment status).

• Did the MTP goals and objectives change 

regarding the priority of congestion 

mitigation and recognition of nonrecurring congestion?

• Did baseline conditions change?

• Are new analytic techniques available?

Below Table 7 summarizes the Getting Started 

Checklist.

Table 7. Getting Started Checklist

No Action to Date

Beginning to Make 

Progress

Partially Achieved

Mostly Achieved

Fully Achieved

Steps and Actions

Update Goals, Objectives and Performance Measures

Have the existing goals, objectives, and performance measures been reviewed?

Have measures been evaluated for compliance with MAP-21 Performance 

Measures for Reliability?

Has stakeholder input and support been gathered/achieved?

Assess Data Needs and Availability

Has the current data collection program been reviewed against reliability data 

requirements?

Have supplemental local and national data sources been investigated?

Have SHRP 2 tools been identified to perform predictions?

Diagnose Causes of Unreliability for Select Facilities

Have current methods for diagnosing reliability problems been investigated?

Have facilities been identified that may be prone to reliability problems?

Have the temporal conditions for reliability analysis been defined?

Have reliability performance measures been calculated?

Have the causes of unreliability by facility been diagnosed?

Evaluate and Prioritize Reliability Strategies

Have current prioritization methods been reviewed for applicability to 

reliability-based evaluations?

Have strategies been identified to address causes of unreliability?

Have benefits, costs and level of impacts been assessed?

Have performance targets been set consistent with MAP-21?

Prepare CMP Update

Has the type of CMP Update been identified (annual or major update)?

Have the necessary steps been taken to perform the update?

47

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer

Chapter 4 Model Congestion Management Plan

Photograph courtesy of Kittelson & Associates, Inc.

Chapter 4 Model Congestion Management Plan

This chapter provides a model congestion 

management plan (CMP) that demonstrates how 

reliability can be incorporated at appropriate steps. 

Addressing reliability and non-recurring congestion 

enhances and expands upon the current state of 

the practice for most CMPs. The model CMP is 

not intended to be a complete document; it is an 

assembly of excerpts intended to provide insight for 

metropolitan planning organization (MPO) developers 

of CMPs.

4.1 One Size Does Not Fit All

Each MPO operates in a unique circumstance, so 

this model CMP should be used as guidance and be 

considered in relation to your region’s population, 

funding, governance, transportation system priorities, 

data availability, and staff capacity. Even if your 

MPO does not assign a high priority to congestion 

mitigation, or has a modest level of recurring 

congestion, the public and their elected officials may 

be supportive of improving the reliability of travel time 

by addressing non-recurring congestion.

4.2 Model Plan Excerpts

The following section shows examples of the 

different CMP components and how reliability can be 

integrated.

This section covers:

• Goals and Objectives

• Performance Measures

• Monitoring Plan

• Problem Identification

• Identification of Strategies

• Implementing Strategies and Monitoring Strategy 

Effectiveness
U.S. Department of Transportation | Federal Highway Administration

48

Chapter 4 Model Congestion Management Plan

Goals and Objectives

MPOs enumerate their goals and objectives in the 

metropolitan transportation plan (MTP), including 

decisions on how to treat congestion mitigation and 

non-recurring congestion. The CMP should incorporate 

these goals and objectives, rather than create a new 

set of priorities.

The following excerpt from the Binghamton (NY) 

Metropolitan Transportation Study’s 2035 Plan [13] is 

an example that gives priority to operational solutions:

Mobility Goal

To create a regional transportation system that 

provides travel choices so personal travel and 

goods movement can maximize efficiency.

Mobility Objectives

Invest in strategies to provide travel choices 

and alternatives to single-occupant vehicle 

personal travel

(1.1) Improve the availability and level of service 

of public transit

Invest in strategies that improve the efficiency 

of vehicle travel 

(2.1) Complete the deployment of the ITS 

Regional Architecture 

• Robust traffic and transit management 

center 

• Pervasive traveler information systems 

• Best available traffic signal system 

technology 

• Incident management on all principal 

arterial highways

(2.2) Participate in statewide and bi-state 

efforts that support ITS Advanced Commercial 

Vehicle Operations

(2.3) Address congested areas with 

appropriate measures, including 

• Improving traffic signal timing 

• Transportation systems management 

strategies

1

2

Source: Binghampton Metropolitan Transportation Study’s 2035 Plan, 

page 15

ITS: Intelligent Transportation Systems

Establishing goals and objectives is the 

first substantive step in the CMP and 

a key entry point for consideration of 

reliability.

The North Central Texas Council of Governments in 

Dallas-Fort Worth demonstrates how a goal from 

the MTP related to system operations can lead to 

objectives for improving operations and reliability can 

be translated into the CMP:

CMP Goal and Actions

Goal: Identify quick-to-implement low cost 

strategies and solutions to better operate the 

transportation system

Action: Implement quick-to-implement low cost 

strategies and solutions to better operate the 

transportation system

Objectives

Reduce SOV trips through travel demand strategies

Provide all users with travel alerts and alternative 

routes in the case of incidents, special events, 

weather, construction, and severe congestion at 

choke points.

Increase the number of intersections that are 

equipped and operating with traffic signals that 

enable real-time monitoring and management of 

traffic flow.

Reduce mean roadway clearance time per incident 

(defined as the time between awareness of an 

incident and restoration) of lanes to full operational 

status

Source: North Central Texas Council of Governments in Dallas-Fort 

Worth CMP (2013), Exhibit III-6

SOV: Single occupant vehicle
49

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer

Chapter 4 Model Congestion Management Plan

Performance Measures

The Moving Ahead for Progress in the 21st Century 

Act (MAP-21) establishes a paradigm of performancebased planning and programming (PBPP) for 

MPOs, transit operators, and state departments 

of transportation (DOTs). They will be required to 

be accountable for their investment decisions by 

measuring the results of project and programmatic 

actions. Performance measures must be credible and 

easily understood by the public and MPO decisionmakers. “Did the money we spent on the Enhanced 

Incident Management Program improve travel-time 

reliability as much as we forecasted?” At right is an 

example from the Delaware Valley Regional Planning 

Commission in Philadelphia, emphasis added, where 

speed drop duration was analyzed over time to 

identify periods of non-recurring congestion.

The Madison (WI) Transportation Planning Board’s 

CMP [15] proposes a larger set of performance 

measures related to reliability. The existing measures 

highlight causes of non-recurring congestion, and 

therefore are only secondary indicators of reliability. 

The preferred measures, to be developed, are a 

more direct metric. Because the CMP is a continuous 

process, it is acceptable to define measures that can 

be developed to improve understanding of outcomes. 

In this case, the MPO shows the resource requirements 

in terms of capital funding and human effort for the 

proposed measures, summarized below in Table 8.

Objectives are supported by 

performance measures that are used 

to track and demonstrate outcomes 

of projects and actions that are 

designed to improve reliability.

Reliability

Archived operations data available through 

the I-95 Corridor Coalition Vehicle Probe 

Project was used to develop a criterion that 

measured reliability. The specific measure 

analyzed was duration of congestion on all 

freeways and select arterials in the region.

The criterion identified road segments during 

the 5:00 to 6:00 PM peak hour, when travel 

speeds dropped below 70 percent of the 

posted speed limit, as well as the duration 

of the speed drop. This analysis produced a 

more robust measure of reliability than what 

was possible in past iterations of the CMP.

Source: Delaware Valley Regional Planning Commission

Table 8. Example of Resource Requirements for Performance Measures from Madison, Wisconsin

Principal Arterial Freeways -Type III (Non-Recurring Congestion)

Measure Resources 

Required

Extent/ Coverage Update 

Frequency

Credibility Public 

Understanding

Decision making

Existing 

Crash reports Currently used High Ongoing High High Low

Service patrol 

reports Currently used Low Low Modest High Low

Preferred

Travel time index 

(TTI)

Capital: 

Programmed

Human: Medium

3 years High High Medium

Incident index Human: High Complete freeway 

coverage Annually High High High

Congestion 

duration

Capital: 

Programmed

Human: Medium

Tri-annually High High Medium

Note: Congestion duration is an important companion measure to TTI, indicating to travelers and decision makers the extent of the peakperiod during which a poor TTI may be encountered.

Source: Madison Transportation Planning Board’s CMP (2011), Table 11
U.S. Department of Transportation | Federal Highway Administration

50

Chapter 4 Model Congestion Management Plan

Monitoring Plan

Performance measurement is a continuous process. 

This is especially true for assessing impacts on 

reliability, where the basis is measuring variability over 

time. The CMP may include a monitoring plan that 

enumerates for each performance measure the agency 

that is responsible for data collection, analysis, and 

archiving; how often the measure will be updated; and 

how it will be reported. 

Table 9 below demonstrates the Performance 

Monitoring Plan from Madison Wisconsin.

A performance based, outcomeoriented CMP must include a plan to 

monitor the transportation system 

and report on improvements to

travel-time reliability.

Table 9. Example of a Performance Monitoring Plan from Madison, Wisconsin

Performance Monitoring Plan

Performance 

Measure

Data Type Collector Analyst Archive Owner Update Cycle

Freeway LOS Freeway volume WisDOT MPO MPO & WisDOT Annually

Freeway Travel Time 

Index

Corridor or 

segment travel 

time

Floating car: MPO

Automated: WisDOT MPO MPO & WisDOT

Floating car: 3 year 

cycle

Automated: 

quarterly

Freeway congestion 

duration

Hourly traffic 

volume

WisDOT,

City of Madison

City, MPO, 

WisDOT

City, MPO, 

WisDOT

Tri-annually on 

selected corridors

Freeway nonrecurring delay 

Crash records Dane County Sheriff, 

TOPS lab WisDOT MPO, WisDOT

Annually

Service patrol 

records

Dane County Sheriff, 

STOC WisDOT MPO, WisDOT

Freeway Incident 

Index

Incident 

location, 

duration, lane 

closure

WisDOT, Dane County 

Sheriff MPO MPO, WisDOT Annually

Source: Madison Transportation Planning Board’s CMP (2011), Table 2
51

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer

Chapter 4 Model Congestion Management Plan

Problem Identification

This example shows how reliability is incorporated 

into the problem identification stage of the process. 

This example is from the Durham-Chapel Hill-Carrboro 

MPO, emphasis added.

Problem Identification

To identify the causes of the problem for the 

reported corridors or intersections, the results 

of the following analyses will be carefully 

reviewed:

• Existing facility analysis (lane 

configuration, signal-timing plan, bus 

loading bay, bicycle/pedestrian facilities, 

surrounding land uses, and driveway 

density),

• Capacity analysis (V/C ratio during a 

peak-hour and daily),

• Intersection LOS analysis (control delay 

during a peak-hour), 

• Corridor analysis (intensity of travel time 

index during a peak-hour and daily),

• Temporal and spatial extension of 

congestion (V/C ratio or travel time index 

during daily), and

• Collision analysis (crash types and 

incident severity during last 5 years)

This comprehensive analysis results will help 

to find the problem causes and lead to the 

development of an improvement strategy.

Source: Durham-Chapel Hill-Carrboro Metropolitan Planning 

Organization

V/C: Volume to Capacity

LOS: Level of Service

This step of the CMP provides the 

MPO an opportunity to identify 

reliability problems related to nonrecurring congestion, based on their 

adopted performance measures.
U.S. Department of Transportation | Federal Highway Administration

52

Chapter 4 Model Congestion Management Plan

Identification of Strategies

The following excerpt from page 48 of the Genesee 

Transportation Council (Rochester NY) CMP [16] is 

a list of strategies for improving freeway operations, 

which should lead to improved reliability.

In this step, the MPO specifies the 

project, actions, and strategies it 

intends to undertake to improve 

reliability.

2. Urban Freeways – Operations

2.A. Incident Management

Definition: Incident management involves the 

coordination of three stages: detection/verification; 

response/clearance; recovery/information. The aim 

of incident management should be to quickly and 

efficiently clear incident scenes without endangering 

first responders or the traveling public. This returns the 

roadway to normal operations sooner and reduces the 

likelihood of secondary incidents. Many incidents are 

vehicle disablements that can be quickly cleared.

Congestion Mitigation Impacts: Reduced incidentrelated delay; fewer secondary incidents.

2.B. Highway Information Systems

Definition: Communicate dynamic information regarding 

existing traffic conditions to travelers en-route on 

the transportation system. These capabilities include 

technologies such as Dynamic/Variable Message 

Signs (DMS/VMS), Highway Advisory Radio (HAR), 

and in-vehicle/handheld systems such as Geographic 

Positioning Systems (GPS) and personal travel 

assistants.

Congestion Mitigation Impacts: Reduced speeds of 

vehicles nearing queues (fewer secondary crashes); 

diversion to alternate routes/modes.

2.C. Ramp Metering

Definition: Ramp meters are modified traffic signals 

placed at the end of highway entrance ramps. This 

controls the flow of vehicles onto highways by breaking 

up platoons of vehicles attempting to enter the highway, 

thus streamlining the merge process. Delays may be 

incurred for ramp traffic, but mainline capacities are 

protected and overall operational efficiency is improved.

Congestion Mitigation Impacts: Increased freeway 

capacity; reduced short freeway trips; increased 

volume/capacity ratio on highways; decreased crash 

rate.

2.D. Highway Pricing Strategies

Definition: Levy fees for driving during peak travel times 

or under congested conditions. Place a surcharge on 

parking in congested areas. Use electronic toll collection 

systems to ease congestion at toll booths.

Congestion Mitigation Impacts: Diversion to alternate 

routes; mode switches; destination changes; increased 

trip chaining.

2.E. Road Work Zone Management

Definition: Manage road work zones to mitigate their 

impact on traffic. Limit work activities to off-peak 

travel hours; phase work activities on a daily, weekly, 

or seasonal basis to minimize traffic impacts; conduct 

a public awareness program in advance of road 

work; identify and promote alternate routes; promote 

ridesharing or transit use.

Congestion Mitigation Impacts: Improved throughput 

around road work zones; minimized vehicle delays and 

speed reductions; reduced crash rate.

Source: Genesee Transportation Council CMP (2013), Page 48
53

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer

Chapter 4 Model Congestion Management Plan

Implementation Strategies and 

Monitoring Strategy Effectiveness 

The following shows how reliability strategies can be 

implemented and monitored to assess effectiveness. 

This example is from the Durham-Chapel Hill-Carrboro 

MPO (emphasis added).

The ultimate purpose of the CMP 

is to create a rational approach to 

mitigating congestion. The policy 

board can weigh the highest priority 

CMP projects and strategies against 

other needs when the MPO develops 

its transportation improvement 

program (TIP).

Chapter 8 - Implementing Strategies 

and Monitoring Strategy Effectiveness

The previously identified improvement 

strategies should be incorporated into the 

regional transportation plan and the TIP. The 

implementation processes of the defined 

strategies will be closely monitored if the 

improvements are adopted in the TIP or other 

program with the financial commitment. The 

implementation of the improvement strategies 

will be led by the operating agencies, and the 

progress should be reported to the MPO every 

month.

The implemented strategies will be monitored to 

assess their effectiveness. Monitoring techniques 

and schedules will be dependent on the type 

of improvement that is implemented, and the 

data availability. It may take years to assess the 

benefits of safety-type improvements that are 

intended to reduce crash rates, crash severity, or 

incidents. Conversely, the benefits of capacity 

improvements are relatively easy to measure and 

assess. Travel time reliability improvements will 

be monitored via the existing data collection 

methods within the region.

The benefits of the implemented strategies 

will be documented in the biannual report. For 

the improvements that may not be accurately 

measured in a two year time frame, results will 

be presented with a description of the limitations 

of monitoring. Capacity projects and other 

improvements that are implemented through non 

CMP methods will still be monitored to determine 

their benefits. Based upon the monitoring results, 

the learned facts will provide feedback for the 

CMP to verify and update the used performance 

measures, the applied data analysis techniques, 

and the considered strategies. If necessary, 

the CMP objectives and the CMP itself will be 

adjusted.

Source: Durham-Chapel Hill-Carrboro MPO “Congestion Management Process: Procedures and Responsibilities Report”, June 2011, p.31

55

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer

Chapter 5 Summary

Photograph courtesy of Kittelson & Associates, Inc.

Chapter 5 Summary

Congestion management is the application of 

strategies to improve transportation system 

performance and reliability by reducing the adverse 

impacts of congestion on the movement of people 

and goods. System reliability is an important objective 

of congestion management that utilizes transportation 

systems management and operations (TSM&O) 

strategies. The application of TSM&O strategies has 

taken on greater significance over the years due to 

constraints on the nation’s transportation system 

expansion. Many regions are experiencing more delay 

due to unplanned disruptions than delay due to peak 

demand, much to the dismay of the traveling public 

and freight shippers.

Until recently, metropolitan planning organizations 

(MPOs) and states that wanted to address travel-time 

reliability had few options for doing so. Data collection 

was expensive and analysis tools were primitive or 

unavailable. However, advances in probe data and 

system detection technologies and new analysis 

tools developed under the second Strategic Highway 

Research Program (SHRP 2) have significantly reduced 

data collection and analysis costs for reliability 

analyses.

The Congestion Management Process (CMP) is one 

of the most-effective ways to improve transportation 

system reliability. Congestion management programs 

are updated frequently and they focus on monitoring 

conditions and developing strategies for alleviating 

congestion. A robust plan that addresses congestion 

in all of its forms, whether recurring or non-recurring, 

results in better system-wide reliability on the 

transportation network.

As of this writing, current Federal transportation 

law, Moving Ahead for Progress in the 21st Century 

Act (MAP-21), identifies a system-reliability goal 

for improving the efficiency of the national surface 

transportation system. CMPs that incorporate 

reliability provide a pathway to developing the 

performance-based planning and programming 

elements that help address legislative needs.

Materials developed by the Federal Highway 

Administration (FHWA), such as this primer and a 

series of training workshops, will help states and MPOs 

create more robust CMPs that result in improvements 

for travelers and freight shippers. Incorporating 

reliability goals, objectives, and performance measures 

into CMPs would respond to the concerns of local 

constituents, result in cost-effective strategies for 

alleviating congestion, and would assist the nation in 

meeting its goal of cost-effectively securing a morereliable transportation system.

57

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer

References

Photograph courtesy of Kittelson & Associates, Inc.

Chapter 6 References

1. Strategic Highway Research Program, 

Transportation Research Board, 

[Online], Available: http://www.trb.org/

StrategicHighwayResearchProgram2SHRP2/

Blank2.aspx. [Accessed 21 June 2014].

2. Institute for Transportation Research and 

Education et al, “SHRP2 L02 - Establishing 

Monitoring Programs for Travel Time Reliability: 

Guidebook Final Validated,” Transportation 

Research Board, Washington, 2012.

3. V. Miller, “American Public Transportation 

Association,” 10 March 2014. [Online]. 

Available: http://www.apta.com/mediacenter/

pressreleases/2014/Pages/140310_Ridership.aspx. 

[Accessed 24 June 2014].

4. United States Department of Transportation, 

“Moving Ahead for Progress in the 21st Century 

Act (MAP-21),” 14 August 2013. [Online]. Available: 

http://www.dot.gov/map21. [Accessed 21 June 

2014].

5. Science Applications International Corporation 

and ICF International, “Advancing Metropolitan 

Planning for Operations—An Objectives-Driven, 

Performance-Based Approach—A Guidebook,” 

Federal Highway Administration, Washington, 

2010.

6. Science Applications International Corporation, 

Kittelson & Associates, Inc. and ICF International, 

“Advancing Metropolitan Planning for Operations: 

The Building Blocks of a Model Transportation 

Plan Incorporating Operations—A Desk Reference,” 

Federal Highway Administration, Washington, 

2010.

7. Cambridge Systematics, “SHRP 2 L05— 

Incorporating Reliability Performance Measures 

into the Transportation Planning and Programming 

Processes: A Guide,” Strategic Highway Research 

Program, Washington, 2013.
U.S. Department of Transportation | Federal Highway Administration

58

References

8. TRB Committee on Highway Capacity and Quality 

of Service, “Highway Capacity Manual 2010”, 

Transportation Research Board, Washington, 2010. 

9. MRI Global and HDR Engineering, Inc, “SHRP 2 

L07—Identification and Evaluation of the CostEffectiveness of Highway Design Features to 

Reduce Nonrecurrent Congestion: Final Report,” 

Transportation Research Board, Washington, 2013.

10. Kittelson & Associates, Inc., “SHRP 2 L08— 

Incorporation of Travel Time Reliability into the 

Highway Capacity Manual: Draft Final Report,” 

Transportation Research Board, Washington, 2012.

11. Kittelson & Associates, Inc., “SHRP 2 L11— 

Evaluating Alternative Operations Strategies to 

Improve Travel Time Reliability,” Transportation 

Research Board, Washington, 2012.

12. Leidos, “Use of Archived Operations Data in 

Transportation Planning: Revised Scan of Current 

Practice,” Federal Highway Administration— 

Saxton Transportation Operation Laboratory, 

Washington, 2014.

13. “Transportation Tomorrow: 2035—Creating a 

Sustainable Future,” Binghamton Metropolitan 

Transportation Study, 2010.

14. “Congestion Management Process—2013 Update,” 

North Central Texas Council of Governments, 

Arlington, 2013.

15. “Congestion Management Process for the 

Madison Metropolitan Planning Area,” Madison 

Transportation Planning Board, Madison, 2011.

16. “GTC Congestion Management Process: Technical 

Documentation,” Genesee Transportation Council, 

2013.

17. ICF International, “Congestion Management 

Process: A Guidebook,” Federal Highway 

Administration, Washington, 2011.
59

Appendix

Appendix: Congestion Management Process Refresher

Readers unfamiliar with the Congestion Management 

Process (CMP) should consult the Federal Highway 

Administration (FHWA) report, Congestion 

Management Process: A Guidebook [17]. This appendix 

provides a very brief overview of the CMP and FHWA’s 

Planning for Operations program so that readers may 

see how the guidance in this primer fits within the 

overall CMP.

The CMP is a systematic approach to provide a 

credible basis for metropolitan planning organizations 

(MPOs) to invest in congestion mitigation across 

modes. The CMP is collaboratively developed with and 

implemented by member agencies. CMPs may identify 

demand reduction or operational management 

strategies to meet Regional Transportation Plan 

objectives. The CMP Actions are illustrated in Figure 

10. The CMP Guidebook can be found online at 

http://www.fhwa.dot.gov/planning/congestion_

management_process/cmp_guidebook/. 

Planning for Operations is also a systematic process 

to help planning agencies, such as MPOs, engage in 

mutually beneficial activities with operations staff from 

other agencies or departments. Engaging operations 

staff drawn from a wide variety of sources, such as 

departments of transportation (DOTs) and transit 

operators, assists the CMP by providing an expanded 

toolbox of management and operations strategies. 

More information can be found at http://ops.fhwa.dot.

gov/travel/plan2op.htm. 

Incorporating Travel-Time Reliability into the Congestion Management Process: A Primer
60

Appendix

Develop Regional

Objectives

Define CMP Network

Develop Multimodal

Performance Measures

Collect Data/Monitor

System Performance

Analyze Congestion

Problems and Needs

Identify and Assess

Strategies

Program and

 Implement Strategies

Evaluate Strategy

Effectiveness

Figure 10. Chart. Actions for the Congestion Management Process

Source: Congestion Management Process: A Guidebook, Figure 2, Federal Highway Administration, FHWA-HEP-11-011.

U.S. Department of Transportation | Federal Highway Administration
Acknowledgments

This primer was developed with the effort of many individuals from transportation and 

planning agencies across the nation. The Federal Highway Administration would like to 

thank the following individuals for their contributions that helped to shape this document:

Eileen Singleton, Baltimore Metropolitan Council (MD)

Greg Stuart, Broward County MPO (Fort Lauderdale, FL)

Chris O’Neill, Capital District Transportation Committee (Albany, NY)

Rita Morocoima-Black, Champaign-Urbana Urbanized Area Transportation Study (IL)

Nabeel Akhtar, City of Charlotte (NC)

Soumya Dey, District of Columbia Department of Transportation

Melissa Ackert, Florida Department of Transportation

Joseph Bovenzi, Genesee Transportation Council (Rochester, NY)

Sarath Joshua, Maricopa Association of Governments (Phoenix, AZ)

Eric Hill, Metroplan Orlando (FL)

Deena Platman, Portland METRO (OR)

Robin Mayhew, Puget Sound Regional Council (Seattle, WA)

Brian Hoeft, Regional Transportation Commission of Southern Nevada (Las Vegas, NV)

Laura Brunn, San Joaquin Council of Governments (Stockton, CA)

James Worthly, San Luis Obispo Council of Governments (CA)

Matt Sibul, Utah Transit Authority

Dean Gustafson, Virginia Department of Transportation

Daniel Blevins, Wilmington Area Planning Council (DE and MD)
The second Strategic Highway Research Program (SHRP2) is a national 

partnership of key transportation organizations that together conduct 

research and deploy products that will help the transportation community 

enhance the productivity, boost the efficiency, increase the safety, and 

improve the reliability of the nation’s highway system. www.goSHRP2.org

U.S. Department of Transportation

Federal Highway Administration

Office of Operations (HOP)

1200 New Jersey Avenue, SE

Washington, DC 20590

www.ops.fhwa.dot.gov

Toll-Free “Help Line” 866-367-7487

Pub. # FHWA- HOP-14-034

February 2015