Smart Congestion Reductions II Reevaluating The Role Of Public Transit For Improving Urban Transportation

This report investigates the role that public transit can play in reducing traffic congestion. Investigates the role that public transit can play in reducing traffic congestion. This analysis indicates that high quality public transit tends to reduce congestion by attracting travelers who would otherwise drive. As public transit service improves on a corridor (including improved speed, convenience, comfort and affordability), congestion levels on parallel roadways tends to decline. Transit investments become more effective at reducing congestion if implemented with complementary road pricing, mobility management strategies and smart growth land use policies. Congestion reduction is just one of many benefits provided by transit improvements. When all impacts are considered, transit investments are often cost effective. This is a companion to the report, Smart Congestion Reductions: Reevaluating The Role Of Highway Expansion For Improving Urban Transportation (www.vtpi.org/cong_relief.pdf). A shorter version of this paper was published as: “Evaluating Rail Transit Benefits: A Comment,” Transport Policy, Vol. 14, No. 1 (www.elsevier.com/locate/tranpol), January 2007, pp. 94-97. Smart Congestion Reductions II: Evaluating Rail Transit Benefits Victoria Transport Policy Institute 2 Introduction Several recent articles criticize urban rail transit investments on grounds that they are ineffective at reducing traffic congestion and financially wasteful (Stopher 2004; Taylor 2004; O’Toole 2004). This paper evaluates this criticism and investigates the role that public transit can play in reducing traffic congestion and achieving other planning objectives. This is a companion to the report Smart Congestion Reductions: Reevaluating The Role Of Highway Expansion For Improving Urban Transportation (Litman 2006b). Context Most industrialized countries have high levels of motor vehicle ownership and extensive roadway systems that provide a high level of service under most conditions. Motorists can drive to most destinations with relative speed, comfort and safety, except under urban-peak conditions. The main transport problems facing most communities are urbanpeak traffic congestion; inadequate mobility for non-drivers; and external costs of vehicle use, including road and parking facility costs, accident risk imposed on others, and various environmental impacts resulting from motor vehicle facilities and use. The question facing policy makers and planners is whether these problems are best addressed by further expanding urban highways to accommodate more vehicle traffic, or instead to emphasize alternative forms of mobility, particular high quality, gradeseparated rail transit designed to attract discretionary travelers (people who would otherwise drive). Many experts argue that major urban transit investments are justified. Critics argue that transit investments are not cost effective, due to their high cost per reduced peak-period automobile trip and therefore cost-inefficient at reducing traffic congestion (O’Toole, 2004; Stopher, 2004). This debate partly reflects differences in how congestion is defined and measured. Traditional planning tended to evaluate transport primarily in terms of motor vehicle traffic, using indicators such as roadway level of service (LOS) ratings, average traffic speeds, and travel time indices, which only reflect roadway travel conditions. From this perspective, transit investments are only valuable to the degree that they reduce motorist delay. However, modern planning tends to use more comprehensive analysis methods that evaluate transport system quality based on mobility (the movement of people and goods) and accessibility (the ease of reaching desired goods, services and activities). Modern planning also tends to give more consideration to other planning objectives besides congestion reduction, and to a wider range of accessibility improvement strategies, including various mobility management strategies and smart growth land use policies. More comprehensive planning tends to place a higher value on public transit investments, particularly when implemented in conjunction with supportive policies such as road and parking pricing, commute trip reduction programs, and transit oriented land use development. Smart Congestion Reductions II: Evaluating Rail Transit Benefits Victoria Transport Policy Institute 3 Transit Congestion Reduction Benefits High quality public transit reduces traffic congestion costs in three ways (Litman, 2005): 1. High-quality, time-competitive transit tends to attract travelers who would otherwise drive (CTS 2009), which reduces congestion on parallel roadways (described in the box below). Various studies indicate that automobile travel times tend to converge with those of gradeseparated transit (Lewis and Williams 1999; Vuchic 1999). How Transit and HOV Reduces Traffic Congestion When a road is congested, even small reductions in traffic volume can significantly increase travel speeds. For example, on a highway lane with 2,000 vehicles per hour a 5% reduction in traffic volumes will typically increase travel speed by about 20 miles per hour and eliminate stop-and-go conditions. Similar benefits occur from traffic volume reductions on congested surface streets. Urban traffic congestion tends to maintain equilibrium. If congestion increases, people change route, destination, travel time and mode to avoid delay, and if it declines they take additional peak-period vehicle trips. Reducing the point of equilibrium is the only way to reduce long-term congestion. The quality of travel options available affects the level of congestion equilibrium: If alternatives are inferior, motorists will resist shifting mode until congestion becomes severe. If alternatives are attractive, motorists will more readily shift mode, reducing the level of congestion equilibrium. Improving travel options can therefore reduce delay both for travelers who shift modes and those who continue to drive. To attract discretionary riders (travelers who could drive), transit must be fast, comfortable, convenient and affordable. In particular, grade-separated transit provides a speed advantage that tends to attract motorists. When transit is faster than driving, a portion of motorists shift until the highway reaches a new equilibrium (until congestion declines so transit’s time advantage attracts no more motorists). The number of motorists who shift may be small, but is enough to reduce delays. Congestion does not disappear but is never as bad as without the parallel grade-separated transit service. Several studies have found that the faster the transit service, the faster the travel speeds on parallel highways (Mogridge 1990; Lewis and Williams 1999; Vuchic 1999). Comparisons between cities also indicate that total congestion delay tends to be lower in areas with good transit service (STPP 2001; Litman 2004a). Shifting traffic from automobile to transit on a particular highway not only reduces congestion on that facility, it also reduces vehicle traffic discharged onto surface streets, providing “downstream” congestion reduction benefits. For example, when comparing highway widening with transit improvements, the analysis should account for the additional surface streets traffic congestion that would be avoided if transit improvement attracts highway drivers out of their cars. 2. Rail transit can stimulate transit oriented development (TODs) – compact, mixed-use, walkable urban villages where residents tend to own fewer cars and drive less than if they lived in more automobile-dependent neighborhoods (“Land Use Impacts On Transport,” VTPI 2005). Before-and-after studies indicate that households often reduce their vehicle travel when they move to transit-oriented locations (Podobnik 2002). 3. High quality transit service can reduce user travel time costs. Even if transit takes more minutes, many travelers consider their cost per minute lower than driving if transit service is comfortable (passengers have a seat, vehicles and stations are clean and safe, etc.) allowing passengers to relax and work (“Travel Time Costs,” Litman 2006a; Litman 2007b). Smart Congestion Reductions II: Evaluating Rail Transit Benefits Victoria Transport Policy Institute 4 Winston and Langer (2004) found that motorist and truck congestion delay declines in cities as rail transit mileage expands, but increases as bus transit mileage expands, apparently because buses attract fewer motorists, contribute to congestion, and do little to increase land use accessibility. Garrett and Castelazo (2004) found that congestion growth rates tend to decline in cities after light rail service begins. Baltimore’s congestion index increased an average of 2.8% annually before light rail but only 1.5% annually after. Sacramento’s index grew 4.5% annually before light rail but only 2.2% after. In St. Louis the index grew an average of 0.89% before light rail, and 0.86% after. Between 1998 and 2003, Portland’s population grew 14%, but per capita congestion delay did not increase, possibly due to rail transit investments that significantly increased transit ridership during that period (TTI 2005). Other studies find similar results (LRN 2001). Baum-Snow and Kahn (2005) found significantly lower average commute travel times in areas near rail transit than in otherwise comparable locations that lack rail, due to the relatively high travel speeds of grade-separated transit compared with automobile or bus commuting under the same conditions. They estimate these savings total 50,000 hours per day in Washington DC, and smaller amounts in other cities. Nelson, et al (2006) used a regional transport model to estimate transit system benefits, including direct users benefits and the congestion-reduction benefits to motorists, in Washington DC. They found that rail transit generates congestion-reduction benefits that exceed subsidies. Texas Transportation Institute data indicate that congestion costs tend to increase with city size, but not if cities have large, well-established rail transit systems, as illustrated in Figure 1. As a result, New York and Chicago have far less congestion than Los Angeles. Figure 1 Congestion Costs (Litman 2004) $0 $200 $400 $600 $800 $1,000 $1,200 0 5,000 10,000 15,000 20,000 City Population (Thousands) A nn ua l D ol la rs P er C ap ita Large Rail Small Rail Bus Only Los Angeles