Strengthening Linkages between Transportation Demand Management and Traffic Management

Introduction

Motivation for the Document

Users of our transportation system expect their travel to be safe, reliable, and seamless. From a traveler’s perspective, the focus on the entire trip, rather than just one section of it, is obvious and necessary. Travelers today want on-the-go travel choices throughout the trip, including the choice of destination (e.g., a park-and-ride lot or work location), mode (e.g., a single-occupancy vehicle [SOV], rideshare, a transportation network company [TNC], or mass transit), route, time of day, and facility or lane type (Table 2).

Table 2. Choices for travelers along a trip.

Type of Choice	Description
Destination choice	Where would the user like to go—home (if the person is teleworking), the work site (including a satellite office or branch location), a recreational site, an event site, a park-and-ride lot, a parking space, etc.?
Mode choice	What type of transportation mode will the user take—SOV, carpool, walk, bicycle, vanpool, bus, train, shuttle, TNC, bikeshare, carshare, microtransit, etc.?
Route choice	Which road(s) will the user take—arterials, highways, local streets, etc.?
Time-of-day choice	When will the user take the trip—off-peak or peak travel hours or when incidents have been cleared?
Facility or lane choice	What specific facility options will the motorist who decides to drive take—the choice of lanes (e.g., high-occupancy vehicle [HOV], high-occupancy toll [HOT], express toll, bus-only, truck-only, and shoulder lanes) or parking facilities (e.g., on-street spaces, garages, and lots).

Enabling travelers to make informed decisions across all of these choices clearly requires a proactive and regionally integrated approach to managing the system across the trip chain, linking different public and private agencies, functions, and roles. The trip chain represents the complete series of decisions made by a traveler throughout a trip from the choice of travel destination to the final choice of facility. Managing the entire trip chain broadly requires two functions:

• Managing the overall travel demand on the system, addressing how and when people need to travel.
• Managing the resultant traffic on the system, addressing how they traverse the system efficiently.

Traditionally, separate unconnected programs are responsible for these functions in a region. For example, a metropolitan area may have a transportation demand management (TDM) program, and several other agencies are responsible for traffic management. The motivation for this compendium is to illustrate the benefit of linking TDM and traffic management programs to achieve the improved outcomes of travel reliability and access. The intent of this compendium is to show how regions have connected demand and traffic management programs to provide enhanced choices to travelers and meet their growing customer expectations.

Nature of the Opportunity

The motivation for this document also stems from the recent revolutions that have occurred in traffic management and travel management. Spurred by greater connectivity (to both the infrastructure and travelers), emerging approaches to TDM and traffic management are blurring the lines between the two functions.

Operating agencies throughout the country have found value in moving from reactive to proactive postures in their system operations. With strategies such as variable speed limits, lane control, dynamic shoulder use, and queue warning, agencies have greatly expanded the toolbox of operational strategies that emphasize reliability of traffic on facilities.

Similarly, the notion of TDM has undergone a very visible revolution, with bicycle and pedestrian considerations, shared-use mobility opportunities, and smartphone usage largely driving the change. Strategies such as new first- and last-mile services, new modal options, personalized travel alerts, multimodal information integration, and advances in TDM have made it possible to provide targeted, actionable information to travelers that was not available even a few years ago.

With these advancements, the lines between what is considered TDM and what is considered traffic management are blurring. Over the last several years, the concept of active transportation and demand management (ATDM) has provided a programmatic framework to combine many of these strategies into a holistic approach to manage for reliability and improve traveler choices (figure 1).

With that comes an opportunity to leverage the advancements in each area to achieve mutually beneficial outcomes. When traffic management and TDM efforts are linked, the transportation specialists can effectively manage traffic that results from travel demand, anticipate and respond to planned and unplanned events, and provide travelers with high quality information about the transportation system.

Figure 2 illustrates the nexus of these functions and identifies areas of collaboration that are possible between the two groups. At the middle of the diagram are the obvious functions that directly concern both groups. For example, both groups use pricing and incentives to influence route, time and mode choices. However, what is not immediately obvious is the connection between the seemingly unrelated functions (say traffic incident management and employer-based outreach services) in the two groups. Through effective collaboration, the impact of a specific function within traffic management can be enhanced with demand management strategies. For example, smarter work zone programs can benefit from targeted employer outreach around the work zone.

Historically, both TDM and traffic management have focused on recurrent congestion. In recent years, the emphasis on reliability has sharply brought into focus the non-recurrent aspect of congestion (e.g., weather, incidents, special events, and work zones). It is in this non-recurrent realm that the greatest and most immediate opportunity for demonstrating linkages for TDM and traffic management exist.

New Possibilities Produced by Linking Transportation Demand Management and Traffic Management Strategies

Traffic managers may think that TDM efforts only provide planning-related strategies that address long-term commute reductions. This is not the case. Increasingly, TDM professionals leverage the connections they have with employers and other organizations to address short-term traffic challenges.

TDM professionals, on the other hand, may think that traffic managers are only concerned with vehicle throughput, not passenger throughput. In fact, many traffic managers are providing a variety of approaches to address traffic challenges.

Traffic managers also bring to the table real-time system conditions data and management of traffic control and restrictions, and are the providers of travel information. TDM professionals arm the traveling public with knowledge of their transportation options and may have unique, lesser-known ways and business models to get information out, especially to targeted populations (e.g., the mobility disadvantaged, employers, transit users, and the freight community).

How do these linkages play out in real life? Table 3 illustrates some potential ideas for how both groups working together can add creative new approaches to managing travel reliability.

Table 3. New possibilities to enhance travel reliability created by integrating TDM and traffic management strategies.

Area	Typical Activities	New Possibilities
Construction	Maintenance of traffic plans developed by the implementing agency, including local mitigation and traffic management practices Outreach, varying by complexity of the project	Temporary priority treatments for buses and HOVs Targeted employer-based outreach Integration of shared mobility services for first- and last- mile services during construction Park-and-ride lot monitoring and information sharing
Weather	Maintenance of roads Communication of travel conditions through 511 and social media	Advance notification of impending weather to travelers and employers Encouraging safer options
Incidents	Communication of incident location and status through travel information channels like 511 and social media Local management of incidents including detours	Local employer outreach about incident conditions Transit impact assessment and coordination
Special events	Parking and wayfinding information Outreach varying by size of the event Local traffic management including use of portable signs and temporary active traffic management	Combination of transit access with event tickets Parking information and reservations Shuttle service coordination
Congestion mitigation	Use of HOV/HOT lanes and ramp metering, and dynamic shoulder use	Provide opportunities for travelers to carpool or utilize roads during non-rush hour traffic Use of first- and last-mile services to support guaranteed ride home programs

For example, the following instances show the value of collaboration between TDM and traffic management:

• Working together to prioritize bus movement through a corridor during periods of highway construction. This allows for greater person throughput and includes strategies such as temporary dynamic shoulder use for specific periods for HOVs and transit.
• Enabling proactive messaging of weather forecasts on dynamic message signs to support time shifts in anticipation of bad weather.
• Temporarily monitoring park-and-ride lot availability and disseminating information during construction to increase transit use.
• Messaging employers in an area affected by a major incident (e.g., a bridge collapse).
• Targeting traveler information messaging around specific special events.
• Providing opportunities for shared use and alternate modes during periods of transit outages.

None of these examples are radical, and in fact agencies around the country routinely consider many of these techniques as they respond to pressing needs such as a winter storm, a transit strike, or a major reconstruction effort. Whether the SafeTrack in Washington, DC, the Pulaski Skyway reconstruction, or the solar eclipse, agencies are using these strategies to achieve their goals.

About this Compendium

This compendium presents 16 case studies organized by seven context areas. Each context represents a different scenario in which TDM and traffic management strategies could be jointly used to improve the travel experience for users, given the conditions. The contexts are:

1. Managing demand and traffic during weather events and natural disasters.
2. Linking TDM and traffic management as part of transit disruption.
3. Incorporating TDM as part of a major road reconstruction project.
4. Managing system efficiency using active demand management and active traffic management.
5. Using HOT and priority treatments for transit service enhancements.
6. Managing special events using parking, TDM, and traffic management.
7. Managing smart parking and considering local traffic management.

One to three case study examples are provided for each context and show how TDM and traffic management were linked to address a specific issue, the strategies implemented, if and how they affect a portion of the trip chain, and the unique successes of those case studies. The symbol(s) for the portion of the trip chain affected are also included at the beginning of the case study. In addition, short vignettes or highlights of other examples of TDM and traffic management integration are also provided for each context.

Intended Audience and Use

This document should be of interest to the following groups of transportation professionals in a region:

• TDM professionals working with departments of transportation (DOTs) or transportation management associations.
• Traffic management professionals working at transportation management centers and DOTs.
• Regional planners and transportation system management and operations coordinators at State and local agencies and metropolitan planning organizations.

The case studies provided in this compendium aim to spur ideas and encourage collaboration between demand management staff and traffic managers around specific areas of interest. The organization of the case studies into the seven contexts provides an entryway and motivation for these professionals to begin conversations with each other. In other words, for regions that might be considering a large construction project or anticipating a transit disruption, the case studies in the compendium provide insights on how agencies can improve their approaches to manage travel reliability during conditions when the transportation network is under stress.

In addition to providing a broad overview of approaches, reviewing the examples provided in this compendium can help regions begin the process of:

• Establishing supportive policies that allow the two groups to work together.
• Creating the ability to make temporary changes to existing programs and systems.
• Finding new communication and partnership strategies that amplify the impact of traveler-focused messaging.