Journal of Transportation Engineering, Part A: Systems

Most studies on traffic assignment ignore the substantial effects of searching for parking on travel times and congestion. Recent work on parking reservation systems provides an alternative to searching for parking by allocating parking spaces while travelers are en route, or before they depart. The necessary technologies are well established and generally available, but the network effects of parking reservation are not yet well understood. By using parking reservation systems, system optimal traffic assignment can be combined with parking space allocation to minimize the combination of in-vehicle travel time and time spent walking from parking to the destination. This paper modifies the linear program for system optimal dynamic traffic assignment of round-trip travel to include parking assignment. The parking location and time spent at the destination affect the departure time and source node for the return trip. The model is further extended to trip chains for travelers visiting multiple zones before returning to their residence. Numerical results quantify increases in walking time and in-vehicle travel time when primary parking is unavailable.

Low-visibility conditions can inhibit a driver’s ability to perceive appropriate operating speeds, particularly during foggy conditions in which the characteristics of the fog can vary spatiotemporally. Numerous agencies have installed countermeasures such as weather advisory systems and variable speed limits (VSLs), but the results have not been analyzed quantitatively. This paper assesses how the I-77 fog VSL system in Fancy Gap, Virginia, affected driver speeds since its activation in October 2016. Prior to implementing the VSL, mean speeds were twice the safe speed based on stopping site distance (SSD) during fog. The VSL system sought to encourage drivers to travel closer to the SSD-based safe speed by posting appropriate reduced speed limits. The results indicated statistically significant reductions in mean speeds after the VSL was activated, and drivers drove closer to the safe speed based on available visibility. Compliance with the posted variable speed limit generally improved once drivers encountered reduced visibilities. Given the short period since activation, insufficient crash data existed to perform a complete safety analysis. However, the preliminary results indicated very promising safety trends for fog-related crashes. The results of this VSL implementation may serve as a reference for other agencies contemplating alternatives to improve safety in fog-prone areas and indicate that the countermeasure had a positive effect.

Using a real-time prediction model of lane-based queue lengths, the authors predicted the lane-based delay using real-time prediction of the incremental queue accumulation (IQA), which can effectively overcome the difficulty of field data collection when using the IQA to calculate the delay. The authors used the Lighthill–Whitham–Richards (LWR) shockwave theory to analyze the IQA changes under different shockwaves. The proposed model was divided into underflow and overflow cases to illustrate the variation of the IQA when a residual queue exists. Two types of delay formulas were considered regarding the effects of the signal offset: coordinated lane and noncoordinated lane delays. The model was tested in a field experiment and compared with the Webster model and the Highway Capacity Manual IQA model, and the results showed that the model has satisfactory accuracy and strong robustness.

Traffic volume prediction plays a critical role in transportation system and infrastructure management. This paper develops the first application of an unobserved component model (UCM) for monthly traffic volume forecasting. We compare the UCM model with simple linear regression, autoregressive integrated moving average (ARIMA), support vector machine (SVM), and artificial neural network (ANN) models based on monthly traffic volume data from a key corridor in New Jersey. As a general econometric method, the UCM decomposes the time series into trend, seasonal, and irregular components, exhibiting superiority for statistically modeling traffic data with cyclic or seasonal fluctuations. The numerical analysis shows that the UCM outperforms all of the other four models and generates reasonably accurate prediction results. This research indicates that UCM can be considered as an alternative approach to modeling traffic volumes.

Traditional merge control strategies cannot yield the expected effectiveness under heavy traffic conditions at freeway work zones because inevitable traffic conflicts resulting from complex merging and lane-changing maneuvers could increase the potential of traffic collisions, induce stop-and-go movements, and degrade the operational efficiency. This paper presents a dynamic control model to optimize the signal operations of a new merge system, the lane-based signal merge (LBSM), which uses lane-based signals or variable signs to give drivers in different lanes the right of way to proceed through the open lane(s) in a work zone area. The control objective is to maximize the work zone throughput. A genetic algorithm is employed to solve the model. Results reveal that the proposed method yields promising work zone operational performance under heavy traffic conditions.

To improve work zone safety by replacing human flaggers, a new Automated Flagger Assistance Device (AFAD) developed by the Missouri Department of Transportation (MoDOT) was investigated through field and driving simulator studies. The MoDOT AFAD configuration, including STOP/SLOW paddles, Red/Yellow lights, and a changeable message sign, was incorporated into a truck-mounted attenuator. Driver behavior measures were collected to compare the effectiveness of the MoDOT AFAD, its alternative designs, and human flaggers. In the field study, the MoDOT AFAD was able to slow vehicle approach speeds and stop vehicles farther back than flaggers. In the driving simulator study, the MoDOT AFAD and its alternative designs significantly reduced average approach speeds and increased the distance between completely stopped vehicles and the AFAD/flagger. Surveys conducted after each study showed that drivers understood the AFAD well and preferred it over flaggers, especially the MoDOT AFAD configuration. Overall, this case study demonstrated that the AFAD has the potential to improve the safety of work zones and workers.

Although motorcycles are the main mode of transportation in many megacities in developing countries, very little research has been conducted on motorcycle operations and related issues. This paper addresses (1) the empirical analysis of the current status of motorcycle ownership and utilization in Ho Chi Minh City, (2) the estimation of the number of motorcycles used in this city, and (3) the analysis and modeling of different transportation policy scenarios. For (1) and (2), the survey results indicate that on average motorcycle ownership (2.33 motorcycles) is higher than that of working-age people in a family (2.29 people). The total number of motorcycles operating in Ho Chi Minh City is estimated to be almost 2 million fewer than that of registered motorcycles. For (3), the results show that each proposed scenario has its own advantage. The demand management policy, which involves either reducing demand via ride sharing or reducing the number of working days per fortnight to 9, is found to be the only single policy that results in little to no adverse impact on total vehicle trips, emissions, fuel consumption, or revenue.