Alternate Route Handbook

3. Alternate Route Planning Process

Figure 3-1. Stakeholder meeting.

INTRODUCTION

The alternate route planning process involves the following three phases:

• Alternate route selection: choosing preliminary alternate routes and evaluating each route to determine the optimal choice.
  
• Alternate route plan development: developing information to incorporate in the alternate route plan, including information on alternate route implementation.
  
• Traffic management planning: planning for information to be disseminated to motorists during implementation and for traffic control, including capacity enhancements needed to accommodate traffic to, from, and on the alternate route.

Figure 3-2 illustrates the three phases and summarizes key steps in the alternate route planning process.

Figure 3-2. Alternate route planning process.

Alternate Route Planning Process

In the early stages of alternate route planning, the lead agency must decide which stakeholders will be involved. A straw (baseline) objective must first be defined by the lead agency. This will aid in the identification of the stakeholders. The scope and scenarios associated with the straw objective will drive the identification of and motivation for stakeholders to become involved in the alternate route planning process.

An inter-jurisdictional, multidisciplinary team ideally provides expertise in key areas necessary to facilitate successful development of an alternate route plan. For example, a transportation agency may know the capacity of each candidate route, while a law enforcement agency may have familiarity with safety and operations problems on each route. If an agency does not have access to a particular planning or operations resource, it may be able to collaborate with another agency that can share the desired resource. For example, a transportation agency may not have access to a GIS database but can collaborate with the agency that maintains the GIS for the region. For these reasons, it is critical that various stakeholders collaborate as a team.

Depending on the characteristics of a local highway system and the quantity and scope of resources available to stakeholders, several actions may apply to a particular step in the process of selecting an alternate route and developing an alternate route plan. Individual actions are presented as either "minimum" or "ideal." Minimum actions are potentially suited to rural jurisdictions. These areas may not have traffic conditions or a dense highway network that warrants the development of an alternate route plan per recommended ideal actions. Involved agencies may also have less equipment and personnel resources available for alternate route planning and plan implementation. Agencies that have additional resources available may follow the ideal actions. Ideal actions allow for the most detailed, scenario-based alternate route plans. These actions are useful for urban/metropolitan jurisdictions with heavy traffic demand, dense highway networks, and expanded resources to dedicate to alternate route planning and implementation. Ideal actions do not represent a "luxury level" of planning and preparation, but instead facilitate a more detailed and expanded planning process.

Phase 1: Alternate Route Selection

The first step in developing the alternate route plan concerns determining the objectives the alternate route must meet. The multi-stakeholder team must develop the system performance and community-based objectives that the preferred alternate route must satisfy before any further planning can take place. Examples of objectives are (1) whether the alternate route is planned as a local or regional route, and (2) whether the alternate route plan will cover a single highway facility, an entire metropolitan area, or an entire State. The Determining Objectives step allows stakeholders to establish collectively their priorities before making decisions that do not address operational and other community-sensitive impacts.

Once stakeholders identify the objectives, they can establish criteria governing selection of preliminary alternate routes. Examples of criteria include the acceptable travel time and proximity of the alternate route to the route from which traffic will be diverted. Following the establishment of alternate route selection criteria, stakeholders should assemble and index available data on potential alternate routes. This data, along with the alternate route selection criteria, allows stakeholders to identify preliminary alternate routes that warrant further consideration.

Once stakeholders select a preliminary set of alternate routes, the agency in charge of the planning effort may then conduct a site visit. The purpose of the site visit is (1) to corroborate the data collected on the candidate alternate routes, and (2) to identify obvious issues that may hinder selection of a particular alternate route. It is important that stakeholders perform the Phase 1 steps in the sequence presented herein to minimize the expenditure of resources for investigating alternate routes that do not meet the criteria for selection or are otherwise infeasible. The number of alternate routes that agencies consider may vary, depending on area type, as well as the characteristics of roadway facilities that connect to the primary route. A rural area may have only one or two potential routes, while a metropolitan area may have several feasible options for each roadway facility section.

After the site visit and any preliminary analysis, stakeholders will decide whether the candidate alternate routes are acceptable based on the established selection criteria. If screening yields no acceptable alternate routes, then stakeholders must return to the Establish Alternate Route Criteria step. The criteria may need to be changed if they are too restrictive. If acceptable alternate routes are identified, then the evaluation process can proceed. If the evaluation process does not produce a suitable alternate route, then stakeholders must again return to the Establish Alternate Route Criteria step. If the evaluation process produces one or more acceptable alternate routes, then stakeholders must select the preferred alternate route. Selection of a preferred alternate route completes the alternate route selection phase. If multiple alternate routes are deemed acceptable, the primary alternate route typically will represent the route having the shortest travel time and/or greatest reserve capacity to accommodate diverted traffic. In turn, candidate secondary and tertiary routes may have longer travel times and/or reduced capacity.

Table 3-1 shows a checklist of steps, categorized either as a minimum or ideal action, for completing the alternate route selection process.

Table 3-1. Checklist of minimum and ideal actions under alternate route selection planning phase

ACTION	TYPE
	MINIMUM	IDEAL
Step 1: Determine Objectives
Determine performance and community-based objectives to guide planning activities and the alternate route selection process.
Step 2: Establish Alternate Route Criteria
Obtain stakeholder consensus on criteria for alternate route selection.
Set detailed criteria for alternate route selection in addition to the relative priority of each criterion.
Step 3: Assemble and Index Data
Use a paper or electronic map to determine the location of roads that may be used as alternate routes and to obtain information on these routes.
Use a GIS map, if available, to obtain detailed information on available routes.
Consult planning organizations for access to travel demand models that can be used for obtaining data.
Consult transportation agencies for information on typical traffic volumes, roadway geometry, signage, and traffic control devices.
Consult law enforcement personnel and/or transit operators for information on traffic operations.
Consult freeway service patrol operators for information on traffic operations and incident frequency.
Step 4: Identify Preliminary Alternate Routes
Obtain stakeholder consensus on at least one preliminary alternate route to be studied further.
Use travel demand models to estimate the traffic volume that will use the potential alternate routes.
Obtain stakeholder consensus on multiple preliminary alternate routes to be studied further.
Step 5: Conduct Alternate Route Site Visit
Conduct a site visit to observe how the candidate alternate routes perform in the "real world" and to determine if these routes meet the selection criteria.
Videotape site visits in order to review the visits at a later time.
Step 6: Evaluate Preliminary Alternate Routes
Conduct a capacity analysis of candidate alternate routes.
Evaluate candidate alternate routes using traffic simulation software, and test a variety of scenarios.
Step 7: Select Preferred Alternate Route
Obtain stakeholder consensus on the selection of the best available alternate route.
Notify (by lead agency) all affected stakeholders about the alternate route selected.
Choose at least two (preferably three) alternate routes, and obtain stakeholders' concurrence on the selection.
Review alternate routes to decide if they are still effective or if a new alternate route should be selected.

Note: Ideal actions may be applied in addition to the minimum actions if conditions warrant and resources permit.

Phase 2: Alternate Route Plan Development

The second phase is alternate route plan development. In this phase, stakeholders must (1) determine alternate route plan content, (2) develop alternate route plan implementation guidelines, and (3) develop guidelines for discontinuing alternate route plan implementation. Table 3-2 shows a checklist of steps, categorized either as a minimum or ideal action, for completing the alternate route plan development process. Adherence to the sequence of the steps in this phase is not as rigid as in phase 1, Alternate Route Selection. Therefore, the lead agency may choose the order that best suits the resources available to develop an alternate route plan.

Table 3-2. Checklist of minimum and ideal actions under alternate route plan development phase

ACTION	TYPE
	MINIMUM	IDEAL
Step 1: Determine Alternate Route Plan Content
Use a paper or electronic map to illustrate the alternate route plan.
Create detailed alternate route maps.
Include detailed information on the alternate route plans on how to implement the alternate route(s).
Include maps showing the location of all supporting ITS equipment.
Supplement alternate route plan maps with written directions.
Include a traffic signal timing plan.
Include a traveler information plan.
Step 2: Develop Alternate Route Plan Implementation Guidelines
Set guidelines for deciding when to implement an alternate route plan. Consider factors such as number of lanes closed, anticipated incident duration, observed traffic conditions, and the time of day/day of week.
Set guidelines for partial implementation of an alternate route plan.
Step 3: Develop Guidelines for Discontinuing Alternate Route Plan Implementation
Determine at least one measurable criterion for deciding when to discontinue an alternate route plan, and base the decision on the available capacity on the mainline from where traffic was diverted and the operation of the alternate route.
Determine detailed guidelines and scenario-based criteria for deciding when to discontinue an alternate route plan.

Note: Ideal actions may be applied in addition to the minimum actions if conditions warrant and resources permit.

Phase 3: Traffic Management Planning

The third phase is traffic management planning. In this phase, stakeholders must (1) determine information dissemination methods to notify motorists of the alternate route, (2) develop information dissemination methods to guide motorists to/from and along the alternate route, and (3) determine traffic control measures, where necessary, to increase the capacity of the alternate route and to improve its operating efficiency. Table 3-3 shows a checklist of steps, categorized either as a minimum or ideal action, for completing the traffic management planning process. Adherence to the sequence of the steps in this phase is not as rigid as in phase one, Alternate Route Selection. Therefore, the lead agency may choose the order that best suits the resources available to conduct traffic management planning.

Table 3-3. Checklist of minimum and ideal actions under traffic management planning phase

ACTION	TYPE
	MINIMUM	IDEAL
Step 1: Determine Information Dissemination Methods to Notify Motorists of the Alternate Route
Use traffic control officers and temporary signage on the primary route to notify motorists that the road is closed and that an alternate route exists.
Use existing information dissemination sources (such as CMSs, highway advisory radio, 511, media, and the Internet) to provide traffic information where appropriate.
Use alternative information dissemination methods (e.g., en-route and pre-trip) to notify motorists of the alternate route in order to reach everyone affected.
If an alternate route is implemented for a long-term period, then consider disseminating information to encourage travelers to (1) switch to public transit as an alternative to driving, (2) modify their trip time or destination, or (3) carpool.
Step 2: Determine Information Dissemination Methods to Guide Motorists Along the Alternate Route
Deploy temporary trailblazer signs along the alternate route to guide motorists along the route. Specify the location of these signs in the alternate route plan. Remove these signs upon discontinuing use of the alternate route.
Install permanent infrastructure (such as route marker signs with electronic changeable arrows or blank-out trailblazer signs) to guide motorists along designated alternate routes.
Use temporary signs configured with a black legend on fluorescent pink background, as optionally assigned by the MUTCD for traffic incident management area signs.
Step 3: Determine Traffic Control Measures to be Implemented on the Alternate Route
If congested conditions develop at signalized intersections, then manually override signal control or modify the existing traffic signal timing plan.
Suspend roadway activities, if possible, along the alternate route to minimize the loss in capacity.
Enforce parking restrictions along the alternate route.
Control ramp operations at alternate route connection points with a freeway facility.
If congested conditions develop at signalized intersections comprising a computer-based traffic signal control system, then implement special traffic signal timing plans from the traffic operations center to support field traffic control.
Use traffic optimization tools to determine the optimal traffic signal timing plans.
If any tolls exist along the alternate route, then suspend tolls during operation of the alternate route.
If the road that traffic is diverted to is a high occupancy vehicle (HOV) facility or has an HOV lane, then temporarily suspend HOV restrictions to allow all vehicles to use the alternate route.
Suspend or modify the timing of ramp meters to prevent excessive queues on the roadway upstream of the primary route. Many ramp metering algorithms have built-in queue adjustment or queue override functions.
If the alternate route has lane control signals, then modify signal indications to allow extra lanes in the direction that the alternate route is being used.
Evaluate the traffic control plan using computer traffic simulation.

Note: Ideal actions may be applied in addition to the minimum actions.

STAKEHOLDER INVOLVEMENT

Each of the steps illustrated in figure 3-2 is discussed in more detail in later chapters of this handbook. Each section begins with a table, listing potential stakeholders and noting their likely participation in a specific phase of alternate route planning and implementation. Note that the same category of stakeholder might have different responsibilities, depending on which agency has the lead role. Therefore, stakeholder roles and responsibilities must be adapted to local needs and planning team organization.

Table 3-4 lists stakeholders that may be involved in the alternate route planning process and the corresponding planning phases that may warrant their participation. The table also indicates stakeholders that may assume an active role in alternate route plan implementation.

Table 3-4. Stakeholder involvement in each phase of the alternate route planning and implementation process

STAKEHOLDER	Alternate Route Selection	Alternate Route Plan Development	Traffic Management Planning	Implementation
Transportation/public works agency
Law enforcement
Fire department
Emergency medical service
Emergency management agency/Homeland security agency
Transit agency
Turnpike/toll authority
Private towing companies
Elected officials
Planning organization
Individuals and community groups
Major incident response team
Freeway service patrol
Media

OVERCOMING BARRIERS TO DEVELOPING ALTERNATE ROUTE PLANS

There exist many barriers that may prohibit a planning team from developing an alternate route plan. Table 3-5 lists some common barriers and provides recommendations for overcoming each cited barrier.

Table 3-5. Overcoming barriers to developing alternate route plans

BARRIER	HOW TO OVERCOME BARRIER
Lack of an adequate alternate route (e.g., geometrics)	If no suitable alternate route is available, then develop more stringent criteria for when to implement the alternate route, such as, only during a long-term closure.
Unknown conditions on the alternate route	Conduct a site visit on candidate alternate routes before selecting a preliminary alternate route(s). Videotape the site visit so that stakeholders may further review it in the office or during future planning team meetings.
Lack of traffic monitoring equipment on alternate route	Choose an alternate route with traffic monitoring equipment, if available. If no such route is available, then conduct alternate route planning in conjunction with the deployment of traffic monitoring equipment on selected roadways. Alternatively, use field personnel, such as law enforcement officers or freeway service patrol operators, to monitor real-time traffic conditions on the alternate route. Manual traffic monitoring requires coordination and constant communication between on-site personnel and the command post or transportation management center.
Possibility of motorists encountering equal or worse level of service on the alternate route	Use closed-circuit television (CCTV) cameras to monitor traffic performance on the alternate route. When the alternate route is extremely congested, divert traffic onto a secondary alternate route. Also, revise traffic signal timings or implement other traffic control measures in order to improve traffic flow on a poorly performing alternate route. If CCTV cameras are not available, then use manual traffic monitoring for this purpose.
Liability concerns if an accident or safety problems occur due to being directed to an alternate route	Do not use a route with known safety problems as an alternate route. Patrol all alternate routes to ensure that motorists are safe.
Public opposition from individuals and community groups	Include community groups in the alternate route planning process. Perform community outreach to educate the public about the alternate route and its benefits. If a community very strongly objects to a particular alternate route, then select another alternate route, if feasible.
Opposition from other agencies	Examine the feasibility of designating a preferred alternate route that encompasses the same jurisdiction (State, county, local) as the main route in order to (1) minimize opposition from other agencies and (2) facilitate efficient operations and traveler information dissemination along the alternate route and at mainline connections. If a preliminary alternate route crosses multiple jurisdictions, then involve other agencies (such as a county or local department of public works) in alternate route selection so that an alternate route agreeable to all stakeholders may be chosen.
Lack of agency human resources to develop alternate routes	Follow the "minimum" actions described in this document if stakeholders do not have sufficient resources to follow the "ideal" actions. Collaborate with other agencies, which may have sufficient funding and personnel.
Possible loss of credibility in CMS messages if an undesirable level of congestion arises on the alternate route	Use CCTV cameras so that an operator can monitor traffic conditions on the alternate route. If the alternate route becomes too congested, then divert traffic to a secondary alternate route or terminate the alternate route plan. Use CMSs to warn motorists of observed congested conditions on the alternate route. If CCTV cameras are not available, then use manual traffic monitoring for this purpose.
Agency perception that there is not a problem that requires diversion	Conduct a study of past traffic incidents to identify the frequency and level of impact on traffic operations when an alternate route is not implemented. Use computer traffic simulation to study traffic during various scenarios (e.g., by location, time of day) involving lane and total facility closure.
Cost prohibitive	Follow the "minimum" action described in this document if stakeholders do not have sufficient funding to follow the "ideal" actions. Collaborate with other stakeholders, who may have more available money, equipment, data, and personnel. For example, if a stakeholder does not have access to a GIS database, then they may collaborate with another stakeholder that does have access.