Introduction to Multi - Modal Transportation Planning Principles and Practices 22

This paper summarizes basic principles for transportation planning. It describes conventional transport planning, which tends to focus on motor vehicle traffic conditions, and newer methods for more multi-modal planning and evaluation. Multi-Modal Transportation Planning Victoria Transport Policy Institute 1 Conventional Transportation Planning Multi-modal planning refers to planning that considers various modes (walking, cycling, automobile, public transit, etc.) and connections among modes. There are several specific types of transport planning which reflect various scales and objectives:  Traffic impact studies evaluate traffic impacts and mitigation strategies for a particular development or project.  Local transport planning develops municipal and neighborhood transport plans.  Regional transportation planning develops plans for a metropolitan region.  State, provincial and national transportation planning develops plans for a large jurisdiction, to be implemented by a transportation agency.  Strategic transportation plans develop long-range plans, typically 20-40 years into the future.  Transportation improvement plans (TIPs) or action plans identify specific projects and programs to be implemented within a few years.  Corridor transportation plans identify projects and programs to be implemented on a specific corridor, such as along a particular highway, bridge or route.  Modeor area-specific transport plans identify ways to improve a particular mode (walking, cycling, public transit, etc.) or area (a campus, downtown, industrial park, etc.). Figure 1 Transport Planning Process (FHWA and FTA, 2007) A transport planning process typically includes the following steps:  Monitor existing conditions.  Forecast future population and employment growth, and identify major growth corridors.  Identify current and projected future transport problems and needs, and various projects and strategies to address those needs.  Evaluate and prioritize potential improvement projects and strategies.  Develop long-range plans and short-range programs identifying specific capital projects and operational strategies.  Develop a financial plan for implementing the selected projects and strategies. Multi-Modal Transportation Planning Victoria Transport Policy Institute 2 Conventional transportation evaluation tends to focus on certain impacts, as summarized in Table 1. Commonly-used transport economic evaluation models, such as MicroBenCost, were designed for highway project evaluation, assuming that total vehicle travel is unaffected and is unsuitable for evaluating projects that include alternative modes or demand management strategies. Table 1 Impacts Considered and Overlooked Usually Considered Often Overlooked Financial costs to governments Vehicle operating costs (fuel, tolls, tire wear) Travel time (reduced congestion) Per-mile crash risk Project construction environmental impacts Generated traffic and induced travel impacts Downstream congestion Impacts on non-motorized travel (barrier effects) Parking costs Vehicle ownership and mileage-based depreciation costs. Project construction traffic delays Indirect environmental impacts Strategic land use impacts (sprawl versus smart growth) Transportation diversity and equity impacts Per-capita crash risk Public fitness and health impacts Travelers’ preferences for alternative modes (e.g., for walking and cycling) Conventional transportation planning tends to focus on a limited set of impacts. Other impacts tend to be overlooked because they are relatively difficult to quantify (e.g., equity, indirect environmental impacts), or simply out of tradition (e.g., parking costs, vehicle ownership costs, construction delays). Conventional transportation planning strives to maximize traffic speeds, minimize congestion and reduce crash rates (generally measured per vehicle-mile) using a well developed set of engineering, modeling and financing tools. Many jurisdictions codify these objectives in concurrency requirements and traffic impact fees, which require developers to finance roadway capacity expansion to offset any increase in local traffic. Alternatives to roadway expansion, such as transportation demand management and multi-modal transport planning, are newer and so have fewer analysis tools. As a result, conventional planning practices support automobile dependency, which refers to transport and land use patterns favoring automobile travel over alternative modes (in this case, automobile includes cars, vans, light trucks, SUVs and motorcycles). In recent years transportation planning has expanded to include more emphasis on nonautomobile modes and more consideration of factors such as environmental impacts and mobility for non-drivers. In recent decades many highway agencies have been renamed transportation agencies, and have added capacity related to environmental analysis, community involvement and nonmotorized planning. Some are applying more comprehensive and multi-modal evaluation (Litman 2012). Transport modeling techniques are improving to account for a wider range of options (such as alternative modes and pricing incentives) and impacts (such as pollution emissions and land use effects). In addition, an increasing portion of transport funds are flexible, meaning that they can be spent on a variety of types of programs and projects rather than just roadways. Multi-Modal Transportation Planning Victoria Transport Policy Institute 3 Figure 2 Four-Step Traffic Model www.mwcog.org/transportation/activities/models/4_step.asp Most regions use four-step models to predict future transport conditions (see Figure 2). The region is divided into numerous transportation analysis zones (TAZs) each containing a few hundred to a few thousand residents. Trip generation (the number and types of trips originating from each TAZ) is predicted based on generic values adjusted based on local travel surveys that count zone-to-zone peak-period trips. These trips are assigned destinations, modes and routes based on their generalized costs (combined time and financial costs), with more trips assigned to relatively cheaper routes and modes, taking into account factors such as travel speeds, congestion delays and parking costs. Transport models are being improved in various ways to better predict future travel activity, including the effects of various transport and land use management strategies. This predicts future peak-period traffic volumes on each route, and identifies where volumes will exceed capacity (based on the volume/capacity ratio or V/C) of specific roadway links and intersections. The intensity of congestion on major roadways is evaluated using level-of-service (LOS) ratings, a grade from A (best) to F (worst). Table 2 summarizes highway LOS ratings. Similar ratings are defined for arterial streets and intersections. Roadway level-of-service is widely used to identify traffic problems and evaluate potential roadway improvements. Figure 3 illustrates a typical model output: a map showing LOS ratings of major regional roadways. Figure 3 Highway LOS Map (PSRC 2008) Multi-Modal Transportation Planning Victoria Transport Policy Institute 4 Table 2 Highway Level-Of-Service (LOS) Ratings (Wikipedia) LOS Description Speed (mph) Flow (veh./hour/lane) Density (veh./mile) A Traffic flows at or above posted speed limit. Motorists have complete mobility between lanes. Over 60 Under 700 Under 12 B Slightly congested, with some impingement of maneuverability. Two motorists might be forced to drive side by side, limiting lane changes. 57-60 700-1,100 12-20 C Ability to pass or change lanes is not assured. Most experienced drivers are comfortable and posted speed is maintained but roads are close to capacity. This is the target LOS for most urban highways. 54-57 1,100-1,550 20-30 D Typical of an urban highway during commuting hours. Speeds are somewhat reduced, motorists are hemmed in by other cars and trucks. 46-54 1,550-1,850 30-42 E Flow becomes irregular and speed varies rapidly, but rarely reaches the posted limit. On highways this is consistent with a road over its designed capacity. 30-46 1,850-2,000 42-67 F Flow is forced, with frequent drops in speed to nearly zero mph. Travel time is unpredictable. Under 30 Unstable 67Maximum This table summarizes highway Level of Service (LOS) rating, an indicator of congestion intensity. Under optimal conditions a grade separated highway can carry up to 2,200 vehicles per hour (VPH) per lane. An arterial with intersections can carry about half that. Table 3 indicates units commonly used to measure traffic. These are generally measured during peak hours. Speed is generally based on the 85 th percentile (the speed below which 85% of vehicles travel). Traffic volumes are also sometimes measured as Annual Average Daily Traffic (AADT), indicating traffic volumes averaged over a year. Table 3 Basic Traffic Units Parameter Typical Units Reciprocal Typical Units Flow Vehicles per hour (Veh/h) Headway Seconds per vehicle (s/veh) Speed Kilometers or miles per hour (Km/h) Travel time Seconds per km or mi (s/km) Density Vehicles per lane-km or mi (veh/lane-km) Spacing Feet or meters per vehicle (m/veh) This table summarizes units commonly used to measure vehicle traffic.