Variable Speed Limits. Review and development of an aggregate indicator based on floating car data.

Changing factors (mainly traffic intensity and weather conditions) affecting road conditions require a suitable optimal speed at any time. To solve this problem, variable speed limit systems (VSL) ? as opposed to fixed limits ? have been developed in recent decades. This term has included a number of speed management systems, most notably dynamic speed limits (DSL). In order to avoid the indiscriminate use of both terms in the literature, this paper proposes a simple classification and offers a review of some experiences, how their effects are evaluated and their results This study also presents a key indicator, which measures the speed homogeneity and a methodology to obtain the data based on floating cars and GPS technology applying it to a case study on a section of the M30 urban motorway in Madrid (Spain)

Robust dynamic traffic assignment for single destination networks under demand and capacity uncertainty

In this article, we discuss the system-optimum dynamic traffic assignment (SO-DTA) problem in the presence of time-dependent uncertainties on both traffic demands and road link capacities. Building on an earlier formulation of the problem based on the cell transmission model, the SO-DTA problem is robustly solved, in a probabilistic sense, within the framework of random convex programs (RCPs). Different from traditional robust optimization schemes, which find a solution that is valid for all the values of the uncertain parameters, in the RCP approach we use a fixed number of random realizations of the uncertainty, and we are able to guarantee a priori a desired upper bound on the probability that a new, unseen realization of the uncertainty would make the computed solution unfeasible. The particular problem structure and the introduction of an effective domination criterion for discarding a large number of generated samples enables the computation of a robust solution for medium- to large-scale networks, with low desired violation probability, with a moderate computational effort. The proposed approach is quite general and applicable to any problem that can be formulated through a linear programing model, where the stochastic parameters appear in the constraint constant terms only. Simulation results corroborate the effectiveness of our approach

Homogeneization effects of variable speed limits.

Changing factors (mainly traffic intensity and weather conditions) affecting road conditions require a suitable optimal speed at any time. To solve this problem, variable speed limit systems (VSL) - as opposed to fixed limits - have been developed in recent decades. This term has included a number of speed management systems, most notably dynamic speed limits (DSL). In order to avoid the indiscriminate use of both terms in the literature, this paper proposes a simple classification and offers a review of some experiences, how their effects are evaluated and their results. This study also presents a key indicator which measures the speed homogeneity and a methodology to obtain the data based on floating cars and GPS technology applying it to a case study on a section of the M30 urban motorway in Madrid (Spain). It also presents the relation between this indicator and road performance and emissions values

Planning for autonomous vehicles : effects and optimal placement of reservation-based intersections in urban networks

Connected and autonomous vehicle (CAV) technologies can revolutionize the way we transport people and goods and may soon be publicly available, however proper planning for these technologies is crucial to their successful integration into our transportation systems. CAVs can reduce following headways and increase roadway capacity and stability, as well as allow for new, more efficient intersection controls with wireless communication capabilities. This work is twofold: (1) evaluating the traffic congestion impacts of AVs and reservation-based intersection control on real large-scale city networks in Texas using DTA and (2) developing methods to find optimal configurations of reservations and signals in a city network. The first part of this thesis evaluates CAV behavior impacts by simulating different mixed CAV and human vehicle (HV) demand scenarios. Results show improvements in network efficiency with increases in CAV penetration. Reservations were observed to perform better than signals in most scenarios. Namely, the Austin downtown network resulted in a 78% reduction in travel time. However, signals outperformed reservations in some high demand cases on arterial networks due to the reservation's first-come-first-serve (FCFS) policy allocating more capacity to local roads, resulting in arterial progression interruption and queue spillback onto close-proximity streets. The discovered paradoxical effects imply that some intersections are better suited for reservation control than others. The second part of this thesis finds and characterizes favorable mixed-configurations of reservation-based controls and signalized controls in a large city network which minimize total system travel times. As this optimization problem is bi-level and challenging, we propose three different methods to heuristically find effective mixed-configurations. The first method is an intersection ranking method uses simulation to assign a score to each intersection in a network based on localized potential benefit to system travel time under reservation control and then ranks all intersections accordingly. The second is another ranking method, however uses linear regression to predict an intersection's localized score. Finally, we present a genetic algorithm which iteratively approaches high-performing network configurations yielding minimal system travel times. We test the methods on the downtown Austin network and find configurations which are less than half controlled by reservation intersections that improve travel times beyond an all-reservation controlled network. Overall, our results show that the genetic algorithm finds the best performing configurations with the initial score-assigning ranking method performing similarly but much more efficiently. We finally find that favorable reservation placement is in consecutive chains along highly trafficked corridors.Civil, Architectural, and Environmental Engineerin