Journal of Transportation Engineering, Part A: Systems

The Texas Department of Transportation (TxDOT) has been deploying work zone intelligent transportation systems (ITS) in an effort to reduce the number of work zone crashes along the Interstate 35 (I-35) corridor. Road construction lane closures on I-35 are typically performed at night when traffic volumes are lower but driver awareness is often reduced. The two systems evaluated were temporary portable rumble strips (TPRS) alone and end-of-queue warning systems (EOQWS) combined with TPRS. The EOQWS consist of portable changeable message signs linked to radar speed sensors to proactively warn drivers of queueing and slowed conditions ahead. The TPRS alone were deployed for work zone lane closures where no queues were expected, and both EOQWS and TPRS were deployed for lane closures expected to cause queueing. The effectiveness of these systems was evaluated over 4 years of deployments and compared to 1 year of no deployments. Both TPRS alone and EOQWS with TPRS were found to cause a significant reduction in the number of crashes under queued conditions, 60 and 53%, respectively. Additionally, the severity of the crashes that did occur was significantly reduced under queued conditions when either treatment was in place.

For the limitation of technology and cost, the in-roadway sensors sparsely deployed on freeway corridors have been common in the past. Currently, such layouts of sensors can barely satisfy data acquisition requirement for freeway traffic management and organization. Thus, how to efficiently utilize the existing deployed sensors and to add additional sensors within the constraint of budget to satisfy the data acquisition requirement needs to be analyzed. This study discusses the allocation of the add-on sensors to make up for the inadequacy of the precision and the coverage of existing deployed sensors. An objective optimization model was developed to identify the locations of the add-on sensors. To solve the model, a genetic algorithm–based optimization program was proposed. A case study of Ning-Hang freeway in China’s Jiangsu province was conducted to demonstrate the utility of the developed methodology. The results demonstrated that the proposed method was efficient in allocating multitype sensors to improve the accuracy of travel time estimation within certain constraints. Travel time estimation error could be decreased by increasing the number of sensors; however, optimizing the locations of sensors is more efficient than just increasing the number of sensors. An optimal value for the number of sensors exists; increasing this value will not improve the estimation accuracy but cause sensor redundancy, and reducing it will affect the estimation accuracy.

The intersection control-type selections for future facilities can be determined by comparison of a common measure of effectiveness that is average control delay. However, rigid comparisons of such measures tend to mislead the decision-making process in practice, since there must be latent factors in quantification. To this end, this paper proposes the performance comparison framework of different transportation facility alternatives using a common quantitative measure. By considering the uncertainties in a quantification process, the proposed framework provides gray areas (i.e., intuitively visualized information, which decision-makers can use to assist in their engineering decisions). The average control delay of two-way stop control, all-way stop control, signal control types, and roundabouts were compared with contour lines of delay differences. It is found that the delay of a roundabout increases rapidly as the traffic demand increases. Hence, a signal control type has the minimum delay level in that case, despite the fact that the roundabout outperforms for most of the low-demand conditions. When the signal timing plan is optimized, this feature becomes evident. With consideration of the margin of error in the delay, a gray area on the minimum delay surface between the signal control and roundabout types enlarges in the low-demand area. The gray areas can be utilized by practitioners to decide the best intersection control type with consideration of construction and maintenance costs over delay reduction benefit.

Automatic counters (e.g., loop detectors) used for the continuous collection of cycling count data are subject to periodic malfunctions, leading to sporadic data gaps. This problem could affect the calculated values of the annual average daily bicycle (AADB) volumes and impact the estimates of the daily and monthly adjustment factors at these count stations. The impacts become more significant when the data gaps take place frequently and/or for long periods. This research addresses the problem of missing cycling traffic volumes at the count stations that experience frequent sensor malfunctions. The main hypothesis is that a strong correlation may exist among the cycling volumes of nearby facilities within a network. This correlation can be used to develop neighborhood models based on the available historical data. This study made use of a data set of more than 14,000 daily bicycle volumes from the city of Vancouver, Canada. The data were collected between 2009 and 2011 at 22 different count stations. A correlation analysis was first undertaken, and the results showed a strong correlation between the cycling volumes at most of the analyzed facilities. Furthermore, a cross-correlation analysis showed that the strongest correlation between each pair of count stations took place at a time lag of zero days (i.e., concurrent data). Accordingly, a correlation threshold was selected and used to define a set of neighbors for each cycling facility. Statistical models were developed to relate the daily cycling volumes of each pair of neighbors. The models were validated; the mean absolute percentage error (MAPE) was used as an evaluation measure. In general, the MAPE was less than 20% for most facilities when a correlation threshold of 0.6 was used to identify neighbors. However, the error dropped to approximately 15% when higher thresholds were used. The concept should prove useful in estimating the missing cycling volumes in a monitoring program or a data clearinghouse implementation.

Customized bus (CB) service, a new type of public transport service, has emerged in many big cities. The few existing research works on CB have been conceptual and descriptive, based on statistical approaches. This paper analyzes the provision of CB by applying analytical approaches based on demand analysis and network modeling. Several alternative travel modes are considered. The choices of mode and route/service are captured by a logit-type formula, and heterogeneous travelers with a discrete set of values of time (VOTs) are considered. Numerical analysis from one idealized corridor indicates that the introduction of CB service could have a significant effect on mode shift, especially for long-distance trips. Three factors, including CB fare, usage of bus lane, and the out-of-vehicle travel time of CB service, are identified that significantly affect the mode shift performance. Another numerical example on a realistic travel corridor in Beijing is conducted to investigate the influence of CB service on social welfare.

Antiram bollard systems (ABS) can effectively prevent vehicle bombs from approaching protected areas and thus reduce the damage from blasts and debris. This paper presents an assessment of the current design limits for determining whether the designed ABS can prevent truck penetration successfully according to SD-STD-02.01, Revision A. Four available crash tests and 69 numerical experiments were assembled for the evaluation. Assessment results showed that the current design limits for either residual angle of inclination of bollard ${\alpha }_r$ or residual height of bollard $H_r$ present poor performances. Numerical investigations showed the failed ABS were penetrated by trucks in two failure modes, and Failure Modes I and II can be determined by ${\alpha }_r$ and $H_r$, respectively. On this basis, an improved design limit is proposed in terms of both ${\alpha }_r$ and $H_r$. In addition, an analytical model for predicting ${\alpha }_r$ and $H_r$ is developed. Two plastic-hinge patterns of ABS were considered in this model. Comparisons between the predictions and experimental results from crash tests and numerical simulations indicate that the improved design limit combined with the developed analytical model predicts the performances of all the ABS accurately and can be used for the structural design of ABS.