Optimization of Variable Speed Limits for Efficient, Safe, and Sustainable Mobility

Abstract

In an envisioned variable speed limit system, speed limits vary strategically and periodically in accordance with traffic and weather conditions to achieve better safety, efficiency, and environmental sustainability on a traffic network. For such a variable speed limit system, a three-objective, bi-level programming model is proposed to design optimal link-specific speed limits that minimize system travel time, number of expected accidents, and traffic exhaust emissions simultaneously for each specific strategic scenario. A solution framework is developed to solve the model that implements a nondominated sorting genetic algorithm and integrates various tools for performance evaluation. The proposed model and solution framework are demonstrated with the road network within the second ring road in Beijing.

Speed limits, speed selection and network equilibrium

“…A key assumption in Yang et al (2012) and subsequent studies (Yang et al, 2013;Wang, 2013) is road users' perfect compliance with the speed limits, which is restrictive in practical situations, as reported in many studies (Kanellaidis et al, 1995;Tarko, 2009;Yannis et al, 2013). For an individual traveler, a higher driving speed may weaken control of car and require a longer stopping distance, naturally raising the possibility of crash involvement.…”

“…The uniqueness conditions of the UE link travel times and link flows were investigated, and the feasibility of using the speed limits as a flow management toll was discussed. In the same spirit, Yang et al (2013) and Wang (2013) undertook further analysis of the network performance with speed limits. Yang et al (2013) established the tri-objective, bi-level optimization problem, aiming to minimize the travel time, accident occurrence and emission simultaneously.…”

“…In the same spirit, Yang et al (2013) and Wang (2013) undertook further analysis of the network performance with speed limits. Yang et al (2013) established the tri-objective, bi-level optimization problem, aiming to minimize the travel time, accident occurrence and emission simultaneously. Wang (2013) also considered the efficiency and equity issues in the implementation of speed limits.…”

Dynamic Speed Harmonization in Connected Urban Street Networks

“…This solution approach is static, which limits the application of approach to dynamic and real-world operational conditions. Yang et al (2013) have proposed a multiobjective bilevel formulation to determine the optimal speed limits in a transportation network. They have formulated a UE traffic assignment in the upper level and introduced a system-wide travel time as a predictive function of speed limit in the lower level along with other objectives on estimated number of accidents and transportation emissions.…”

Effectiveness of variable speed limits considering commuters’ long-term response

“…In contrast to the abundant literature on VSLs that mainly focuses on their localized impacts on traffic flow and microscopic behaviors of drivers, this study examines VSL systems from an equilibrium perspective and considers individual travelers' long-term response to VSL systems. Attempts have been made to investigate how speed limits reallocate traffic flow across a network in an equilibrium manner (e.g., Yang et al, 2012Yang et al, , 2013bWang, 2013). However, when variable or time-varying speed limits are concerned, the reallocation effect on traffic would no longer be limited to the spatial dimension, e.g., the choice of routes, but also the temporal dimension, e.g., departure-time choices.…”