High occupancy vehicle lanes: Not always more effective than general purpose lanes

Real data show that reserving a lane for carpools on congested freeways induces a smoothing effect that is characterized by significantly higher bottleneck discharge flows (capacities) in adjacent lanes. The effect arises because disruptive vehicle lane changing diminishes in the presence of a carpool lane. The effect is reproducible across days and freeway sites: it was observed, without exception, in all cases tested.Queueing analysis shows that the effect greatly reduces the times spent by people and vehicles in queues. By ignoring the smoothing effect at one of the sites we analyzed, for example, one would predict that its carpool lane increased both the people-hours and the vehicle-hours traveled by well over 300%; when in reality the carpool lane and its attendant smoothing reduced both measures. The effect is so significant, in fact, that even a severely underused carpool lane can in some instances increase a freeway bottleneck's total discharge flow. This happens for the site we analyzed when carpool demand is as low as 1200 vph. It follows that strategies designed to induce smoothing by other means also hold promise for managing congestion, both for freeways that have carpool lanes and those that do not. Possible strategies of this kind are discussed.

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“…Let us now see what a conventional analysis (wrongly ignoring the smoothing effect) as in Dahlgren (1998Dahlgren ( , 2002 and Kirshner (2001) …”

Section: The Real Impacts Of Carpool Lanes On People and Vehicle Delaymentioning

confidence: 99%

The smoothing effect of carpool lanes on freeway bottlenecks

Cassidy

Jang

Daganzo

2010

Transportation Research Part A: Policy and Practice

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“…Sparks and May (1971) developed a mathematical model to evaluate priority lanes for high occupancy vehicles on freeways. Later, Dahlgren (1998) and Daganzo and Cassidy (2008) studied how different modes use freeways, recognizing that if different modes serve different numbers of passengers, then analyses should not consider all vehicles with the same weight. But these works are limited to small scale systems.…”

Section: Introductionmentioning

confidence: 99%

On the distribution of urban road space for multimodal congested networks

Zheng

Geroliminis

2013

Transportation Research Part B: Methodological

121

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a b s t r a c tTransport systems in real cities are complex with many modes of transport sharing and competing for limited road space. This work intends to understand how space distributions for modes and interactions among modes affect network traffic performance. While the connection between performance of transport systems and general land allocation is the subject of extensive research, space allocation for interacting modes of transport is an open research question. Quantifying the impact of road space distribution on the performance of a congested multimodal transport system with a dynamic aggregated model remains a challenge. In this paper, a multimodal macroscopic fundamental diagram (MFD) is developed to represent the traffic dynamics of a multimodal transport system. Optimization is performed with the objective of minimizing the total passenger hours traveled (PHT) to serve the total demand by redistributing road space among modes. Pricing strategies are also investigated to provide a higher demand shift to more efficient modes. We find by an application to a bi-modal two-region city that (i) the proposed model captures the operational characteristics of each mode, and (ii) optimal dynamic space distribution strategies can be developed. In practice, the approach can serve as a physical dynamic model to inform space distribution strategies for policy makers with different goals of mobility.

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“…According to an analysis by the U.S. Census Bureau (2004), the share of people carpooling was 12.2 percent in 2000, which accounts for the second largest share: 77 percent of people drive alone; 4.7 percent use public transit. 1 Recently, however, single occupancy vehicle drivers complain about underused HOV lanes, and many transportation researchers also criticize HOV lanes for their poor e¤ectiveness in easing congestion. Employing a dynamic queuing model with discrete choices, Dahlgren (1998) argues that adding a regular lane to existing lanes is more e¤ective in reducing delay costs than adding an HOV lane in most cases.…”

Section: Introductionmentioning

confidence: 99%

Carpooling and congestion pricing: HOV and HOT lanes

Konishi

Mun

2010

Regional Science and Urban Economics

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It is often argued in the US that HOV (high occupancy vehicle) lanes are wasteful and should be converted to HOT (high occupancy vehicles and toll lanes). In this paper, we construct a simple model of commuters using a highway with multiple lanes, in which commuters are heterogeneous in their carpool organization costs. We …rst look at the HOV lanes and investigate under what conditions introducing HOV lanes is socially bene…cial. Then we examine whether converting HOV lanes to HOT lanes improves the e¢ ciency of road use. It is shown that the result depends on functional form and parameter values. We also discuss the e¤ect of alternative policies: simple congestion pricing without lane division; and congestion pricing with HOV lanes. The analysis using speci…c functional form is presented to explicitly obtain the conditions determining the rankings of HOV, HOT, and other policies based on aggregate social cost.

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High occupancy vehicle lanes: Not always more effective than general purpose lanes

Cited by 62 publications

References 6 publications

The smoothing effect of carpool lanes on freeway bottlenecks

The smoothing effect of carpool lanes on freeway bottlenecks

On the distribution of urban road space for multimodal congested networks

Carpooling and congestion pricing: HOV and HOT lanes

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