Predictive Dynamic Speed Limit in a Connected Environment for a Weather Affected Traffic Network: A Case Study of Chicago

Abstract

Dynamic speed limits (DSLs) are used to improve safety and mobility on freeways in unfavorable traffic conditions due to recurring congestion, roadworks, incidents, or adverse weather. The evaluation of in-field deployment reveals that the effectiveness of DSLs can be hampered by low compliance rates or lack of inherent capacity. With the emergence of vehicle-to-vehicle (V2V) or vehicle-to-infrastructure (V2I) communication, it is believed that the operation of DSLs will be able to take advantage of vehicle connectivity. In this paper, the effectiveness of the predictive DSL operation in a connected environment is investigated on the weather affected traffic network of Chicago city under different operational conditions. For the sensitivity test, different market penetration rates of connected vehicles are tested in microsimulation. Microscopic models are used to simulate information exchange by V2V or V2I communication. However, such an application over a large network with mixed traffic can be computationally expensive. A mesoscopic or macroscopic tool is needed that can scale and be computationally economical at the network level. This study integrates the microscopic aspect of V2V communication and the macroscopic for dynamic traffic assignment at a network level. The evaluation of effectiveness at network level is conducted by the Traffic Estimation and Prediction System (TREPS), which is a mesoscopic simulator. The results show, depending on the strategy applied, meaningful increases in both throughput and prevailing speed.

Estimating the Safety Effects of Congestion Warning Systems using Carriageway Aggregate Data

“…Over time, these systems have been improved with more accurate and lanespecific loop detectors; and more diversified lane-specific messages, but the essence has not changed. What has changed is that in some cases these CWS (both sensors and variable message signs) are also used for different purposes, for example, for speed homogenization or pro-active congestion management with dynamic speed limits (2,3). With the arrival of alternative sensing systems (other than loops), and the possibility of using the vehicle itself as both sensor and actuator, one of the key questions for road operators today is whether continuous investments in infrastructure-based CWS is a costeffective strategy for the near-term (and longer term) future.…”

Development of a Connected Vehicle Dynamic Freeway Variable Speed Controller

“…Future studies should consider a larger test network and selection of the optimal detector locations. Mittal et al used a traffic estimation and prediction system relying exclusively on a mesoscopic simulator to estimate traffic conditions [10]; such models provide limited traffic operations details [11]. Many research efforts have combined control and estimation using Model Predictive Control (MPC) to predict and adjust vehicles' speeds as they move on the bottleneck's upstream link [12]- [14].…”

“…In addition, using MPC methods requires adequate state prediction accuracy, which is difficult when capacity drop-induced nonlinearity occurs. It is also important to note that most VSL research efforts have focused on small freeway sections [2], [10], [16].…”

“…Data must be collected for the VSL to properly function; this data could be from loop detectors or probe vehicles. Mittal et al's work [10] assumed real-time information would be collected from sensors across the entire corridor, which is costly to implement. Tajalli and Hajbabaie [14] used probe vehicles, with 100% CAV market penetration rate, using linearized models and constraints.…”

Exploring the Impact of Differentiated Per-Lane Speed Limits on Traffic Safety of Freeways with Considering the Compliance Rate

“…In fact, the existing studies in the field of speed limit settings paid heavy attention to variable speed limits [6][7][8][9][10] including the cooperative variable speed limit system [11,12], speed limit strategies [13][14][15], speed limit compliance [16], and the impact of speed limits on traffic safety [17][18][19] and traffic performance [20]. In recent years, the studies focusing on variable speed limits under connected-vehicle environments are also highlighted [21,22]. Those studies have made a tremendous contribution to the state of the art, but none of them allowed the speed limit values varying across different lanes.…”