Evaluation of speed limit management on C-32 highway access to Barcelona

Abstract

In July 2007, the Autonomous Government of Catalonia passed a 73-measure plan to improve the air quality in the metropolitan region of Barcelona, Spain. This plan (which turned into law in January 2008) included 80 km/h speed limitations on major highways around the city (e.g., the C-32 highway). One year later, dynamic speed limits (DSL), maintaining the maximum speed limit of 80 km/h, became operational. The objective of the present paper is the evaluation of this policy, what requires a quantitative analysis in terms of congestion reduction, vehicles‟ emissions and traffic safety. As the comparison between different scenarios must be performed with homogeneous traffic demands (i.e., same productivity), comparisons from direct empirical measurements are not representative. Note that during the period of analysis, the huge economic recession arrived to Spain resulting in a clear reduction of mobility demands. CTMSIM macroscopic traffic simulator [1, 2] was applied instead, simulating different scenarios under the same demand. Data in order to construct the baseline demand scenario were collected from double loop detectors installed in each lane along 14.5km of the C32 highway, accessing Barcelona. A quantitative evaluation of the social profitability of this policy in terms of travel times, emissions and safety benefits is provided in the paper. In addition, some guidelines for the construction of homogenous demand scenarios suitable for comparisons, the characterization of fundamental diagrams, the macroscopic model of the highway based on the cell transmission model (CTM) [3, 4], and the definition and assessment of the different elements constituting the objective function in monetary units, are also described. It is concluded from the discussion, that the speed limit management on metropolitan highways accessing to large cities, cannot provide in case of isolated application significant benefits.