Abstract

Most special-use freeway lanes in the US, whether reserved for carpools, toll-paying commuters or both, are physically separated from the adjacent regular-use lanes by some form of barrier. Vehicle movements in and out of a special lane of this type are permitted only at select access points along the route. The barrier at each select point might open for a distance of 400 m or so. Limiting access in this way is said to reduce the “turbulence†that might otherwise occur were the special lane not to have a buffer, such that vehicles could instead enter or exit that lane anywhere along its length. Yet, real freeway traffic studied in spatiotemporal fashion shows that access points are prone to become bottlenecks. The problem occurs when traffic in the regular lanes becomes dense, as commonly happens during a rush. Drivers then seek refuge in the special lane in greater numbers. Since the vehicular maneuvers through the access point are focused within a limited physical space, they can become disruptive and further degrade traffic. Degradation can occur both in the special lane and in the adjacent regular ones. The damage can be worse than what occurs when barrier are not used to limit special-lane ingress and egress. Policy implications are discussed.

Abstract

Managed lanes operations refer to multiple strategies for recurring congestion control by increasing the road capacity or adapting its configuration to the demand level. As a result, the evaluation of their impacts usually focuses on congestion or safety-related indicators. However, with the growing prosperity, consumers demand higher quality transport services, for which reliable transport networks are central. This paper is focused on the travel time reliability assessment of a managed lane experience from a French motorway. The paper shows results from the field test experience of the hard shoulder dynamic use on the A4-A86 motorway in the east of Paris. Further to the reliability assessment, the paper focuses on the reliability indicators. It particularly shows the weakness of the skew of the distribution of travel time indicator.; La gestion dynamique des voies fait appel à de multiples stratégies pour maîtriser les congestions récurrentes, ce en accroissant la capacité de la route ou en adaptant sa configuration à la demande. Ces stratégies sont donc logiquement généralement évaluées en termes d'impacts sur la fluidité ou la sécurité du trafic, impacts mesurés par des indicateurs. Cependant, avec la prospérité croissante, les consommateurs demandent une amélioration de la qualité de service pour laquelle la fiabilité des réseaux de transport est centrale. Cette communication porte sur l'évaluation de la fiabilité des temps de parcours résultant d'une expérimentation de gestion dynamique des voies sur une autoroute en France - le tronc commun A4-A86, à l'est de Paris. La bande d'arrêt d'urgence y a été ouverte à la circulation à certaines périodes de la journée. Les résultats de cette expérimentation sont donnés ici ; à la lumière de ces résultats notamment, les indicateurs de fiabilité sont ensuite discutés. On montre en particulier la faiblesse de certains indicateurs fondés sur la largeur ou la dissymétrie de la distribution des temps de parcours. Document type: Conference object