Abstract
The ever-increasing travel demand outpacing available transportation capacity especially in the U.S. urban areas has led to more severe traffic congestion and delays. This study proposes a methodology for intersection signal timing optimisation for an urban street network aimed to minimise intersection-related delays by dynamically adjusting green splits of signal timing plans designed for intersections in an urban street network in each hour of the day in response to varying traffic entering the intersections. Two options are considered in optimisation formulation, which are concerned with minimising vehicle delays per cycle, and minimising weighted vehicle and pedestrian delays per cycle calculated using the 2010 Highway Capacity Manual (HCM) method. The hourly vehicular traffic is derived by progressively executing a regional travel demand forecasting model that could handle interactions between signal timing plans and predicted vehicular traffic entering intersections, coupled with pedestrian crossing counts. A computational study is conducted for methodology application to the central business district (CBD) street network in Chicago, USA. Relative weights for calculating weighted vehicle and pedestrian delays, and intersection degrees of saturation are revealed to be significant factors affecting the effectiveness of network-wide signal timing optimisation. For the current study, delay reductions are maximised using a weighting split of 78/22 between vehicle and pedestrian delays.
Highlights
1.1 BackgroundThe population growth and economic development have resulted in travel demand increase, especially in urban areas
The effectiveness of signal timing optimisation is measured by percentage reductions in vehicle delays measured in seconds per vehicle per cycle, or reductions in weighted vehicle and pedestrian delays measured in seconds per traveller per cycle
This study has proposed a methodology for network-wide intersection signal timing optimisation over a 24-hour daily period
Summary
1.1 BackgroundThe population growth and economic development have resulted in travel demand increase, especially in urban areas. With the pace of transportation capacity expansion falling significantly behind the level of travel demand escalation, many urban street networks in the United States are currently operated close to, or even over capacities in the AM and PM peak periods. Owning to land scarcity in urban areas and prohibitively high costs of facility delivery, expanding the capacity of an urban street network is typically not feasible. The ever-increasing gap of capacity shortage in the urban street network has exacerbated recurrent urban traffic congestion in peak periods that is increasingly becoming one of today’s biggest challenges. To slow down the deteriorating trend of urban traffic conditions, improving the utilisation efficiency of the existing capacity of an urban street network has been gradually thought of as a possible solution [1, 2]. One of the related measures is to reduce delays experienced by individual travellers at intersections that are affected by intersection signal timing plans deployed in the urban area
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