a collage of eight photos showing a stakeholder meeting, people boarding a bus, a changeable message sign displaying the message race traffic, cars traversing a roadway where barricades delineate travel lanes, a closed-circuit television camera, a crowd of people standing near a train and traversing a pedestrian overpass, two implementation plans, and three traffic management team personnel gathered around a laptop computer

Managing Travel for Planned Special Events

Table of Contents

Chapter Six. Traffic Management Plan
Page 3 of 9

Analysis and Modeling  handbook section pertains to transportation engineer, law enforcement officer, and event planning user groups

Overview

No planned special event transportation management plan, not even for a repeated special event, can be prepared and executed without detailed planning and without modifications as the event unfolds. To be successful, the event planning team has to anticipate, and therefore plan for, all the possible scenarios that will challenge the transportation network and the mobility of the plan.

A special event transportation and implementation plan includes elements such as personnel assignments, communications from various sources, communications between multiple agencies, and guidelines for accessing and utilizing remote equipment. All of these elements are used in various manners depending upon the existing conditions, and the plan should be flexible to allow modification throughout the event. In essence, a special event plan is a plan for multiple contingencies and multiple scenarios.

Many tools and techniques are available to analyze and assess the plans. Most are scenario-based and use techniques to simulate the event to ensure that the proper resources and communication protocols are in place and are efficient. These techniques address the many contingencies, and as such, numerous plans are developed prior to the event and implemented during the event, as they are needed.

It is important to note that the assessment and development of plans do not end when the event ends. At the conclusion of the event, stakeholders comprising the event planning team and traffic management team must evaluate the plan in order to improve the plan as well as to utilize the lessons learned in future traffic management applications. Further, this evaluation process is not restricted to post-event, but instead can and should be conducted throughout the event, and modifications to the plan made on-the-fly.

Analysis Techniques

Planners historically have used simple planning techniques as well as high-tech computer-assisted techniques to plan and manage for planned special events. These planning techniques take many forms, ranging from traditional incident management processes and traffic engineering processes to computer modeling of scenarios.

Three primary ingredients for successful event management are: (1) proper resources, both human and non-human, (2) a good communications plan (implementation plan), and (3) a firm understanding of the transportation system's capabilities and, more importantly, its limitations. The best and most proven techniques for event operations planning are to model and test the scenarios using any and all contingencies.

Tabletop Exercises

Tabletop exercises bring all of the stakeholders together. During these exercises, scenarios are posed and escalated. These scenarios typically do not require modeled network information, as their primary purpose is to test the stakeholders as to how they would react and to fine tune the responsibilities of each stakeholder and the communications protocol between the stakeholders. Many scenarios that can cause disruptions to the event transportation are played out, and any loopholes in the operations planning are obvious to the participants. This type of exercise is supported by more detailed analyses, usually in the form of computer simulation.

Computer Traffic Simulation

In large-scale event planning, it is beneficial to understand the impact that the event will have on the existing roadway system. Where this network is complex and multiple alternatives may exist, each will need to be evaluated. The common approach to this function is to apply tools to model the network. Capacity and LOS analyses are useful tools for gauging the expected operating conditions along roadway segments and for determining the "order-of-magnitude" changes that will result from major changes in traffic flow (e.g., as caused by a planned special event) and roadway improvements (e.g., widening, bottleneck improvements). However, improvements provided by transportation management strategies and systems are typically not reflected in such procedures. Moreover, information on performance measures (e.g., vehicle delays, fuel consumption, emissions) is not provided by capacity analysis techniques. It may therefore be worthwhile to utilize computer traffic simulation models, which can examine the manner the roadway network performs under various sets of simulated conditions.

As implied by the name, traffic simulation models examine the manner in which the roadway network performs under various sets of "simulated" conditions. They provide an excellent means of estimating changes in roadway performance metrics (e.g., average speeds, travel time, delays, emissions) resulting from increased traffic, roadway restrictions, traffic management strategies and improvements.

Traffic simulation models can be divided into the following two general classes:

  • Macroscopic models are based on deterministic relationships between roadway and intersection characteristics and traffic flow. Examples include TRANSYT-7F, FREQ, and the TRAF suite of models.
  • Microscopic models simulate the movement of individual vehicles through the network being modeled. Examples include INTEGRATION, Paramics, Synchro/SimTraffic, and the TSIS suite of models.

Some simulation models are designed for analysis of individual intersections or specific types of facilities, while others are designed for network-level analysis. Models capable of network-level analysis include TRANSYT-7F, Synchro/SimTraffic, INTEGRATION, and Paramics. The TSIS (Traffic Software Integrated System) set of models includes NETSIM for network analysis, FRESIM for freeway analysis, and CORSIM, which is an integrated package of the network and freeway models. The TRAF set of models includes NETFLO for network analysis, FREFLO for freeway analysis, and an integrated package (CORFLO) of the network and freeway models. FREQ simulates corridor traffic operations including one freeway and one parallel arterial.

The individual models vary in their capabilities, limitations, and ease of use (a discussion of which is beyond the scope of this Handbook). A significant amount of effort generally is required to learn to use traffic simulation models, including setting up the appropriate inputs and parameters. A significant amount of effort may also be required to obtain traffic and network data to conduct the analysis and to calibrate the model to local conditions. Data requirements are proportional to the extent of the network being modeled. The required data can include characteristics of each link (e.g., length, number of lanes, auxiliary / HOV lanes, ramps, grade, speed limits, lane widths, pavement condition), link traffic flow information (e.g., entering / exiting volumes, ramp volumes, travel times, percent heavy vehicles and buses, lane changing characteristics) and other types of information such as detector locations, incident characteristics (e.g., effect of lane blockage on capacity), and ramp metering operations.

Simulation models generally require a non-trivial analysis effort. Moreover, any model-specific limitations should be taken into consideration when interpreting the outputs of simulation. Sensitivity analyses are important to developing an understanding of: (1) how reasonable the simulation estimates are and (2) how much confidence the analyst should place in them.