The increasing number of midblock vehicle–pedestrian crashes has led traffic engineers to consider safer treatments for pedestrian crossings while preserving flow efficiency. One of the existing solutions is to install signalized crosswalks. Using a microsimulation approach, this study first assesses three signal systems for a typical midblock crosswalk (MBC) with varied geometries, with the aim to explore how different signalization schemes and crosswalk geometries affect measures of effectiveness from all user perspectives. The results indicate that two-phase timing outperforms one-phase timing and the innovative high-intensity activated crosswalk significantly improves vehicle operations over actuation by pedestrians and pedestrian light control. Of existing signals, the pedestrian user-friendly interface (PUFFIN) is more functional because of its dynamic pedestrian clearance interval, but it still does not account for enough safety and human factors in its control logic and thus lacks an adaptive ability in fulfilling competing objectives. Fuzzy logic control (FLC) has proved effective for a complex optimization problem with multiple goals, uncertain information, and vague decision criteria. Traffic signal timing lies in this realm. To model the range of variables affecting MBCs, a user-friendly FLC counterpart is developed and then evaluated against PUFFIN to quantify potential safety and efficiency benefits. The results show that with straightforward logic and tractable parameters, FLC manages the MBC signal timing effectively and outperforms PUFFIN in terms of a compromise among enhanced safety, ameliorated operations, and lessened social cost from crashes and delays.

A cross-median crash (CMC), in which a vehicle crosses the median, is one of the most severe crashes because of the risk of colliding with an opposing vehicle. Ordinal discrete choice modeling efforts for investigating the nexus between the underlying severity propensity and miscellaneous roadway-safety-related factors for single- and multivehicle CMCs that occurred from 2001 to 2007 in Wisconsin are described. Ordinal logit (ORL) and probit (ORP) models were employed for the severity analyses. For multivehicle CMCs, the final ORP model found that road condition has a significant effect on severity. Adverse road conditions enhance the likelihood of a more severe consequence if a CMC occurs. Winter precipitation negatively affects CMC severity, and logically Wisconsin's geographical location plays a significant role. The final ORL model found that alcohol and drug use incurs more severe consequences when a CMC occurs. Both models found that more severe injuries occur on roadways posted with higher speed limits. The similarity and dissimilarity in findings by both models imply that it is necessary for safety researchers to apply distinct statistical methods when pursuing a comprehensive understanding of a study topic. The final ORP model for single-vehicle CMCs shows that alcohol and drug use, lane curvature, and unfriendly lighting conditions exacerbate the severity tendency if a CMC happens. A dry road surface is found to incur more severe consequences; this result implies that more severe single-vehicle CMCs are closely related to maintaining overly high speeds. All ORL regression models for single-vehicle CMCs were found statistically invalid. Median width and average daily traffic were found insignificant for both multivehicle and single-vehicle CMCs.

The widespread emergence of modern roundabouts in North America has kindled a controversy about pedestrian access. Almost uninterrupted traffic streams, ambient noises, and urban settings make it difficult for the visually impaired to perceive safe crossing gaps when only auditory cues are used. In 2005, the U.S. Access Board released a revised draft guideline calling for the provision of a “pedestrian-activated traffic signal … for each segment of the crosswalk” to ensure access for vision-impaired pedestrians. The Access Management Manual prescribes major transportation actions encompassing multimodal streets with sidewalks and adequate pedestrian refuges, but the manual does not address the issue of pedestrian access at roundabouts. In North America few roundabouts have been outfitted with pedestrian signals. Little research has explored signalizing roundabouts for pedestrian access improvements. This simulation study quantitatively assessed the performance of four pedestrian signals placed at roundabouts with a wide spectrum of test scenarios resulting from varied crosswalk layouts, installation schemes, and operational conditions. A two-stage installation scheme was found more operationally efficient than a one-stage scheme; with the two-stage scheme, no significant differences existed between three layouts. When a one-stage scheme operated, a distant layout reduced vehicle delay and queue length because of enlarged storage space. High-intensity activated crosswalk signals induced minimum vehicle delay, and pedestrian user-friendly interface signals minimized pedestrian delay while fully protecting pedestrians. The findings provide an objective basis for identifying crosswalk treatments to improve roundabout accessibility and are informative for transportation policy makers, planners, and practitioners in the access management community who work at enhancing roundabout accessibility for pedestrians.

One critical issue of traffic control is the optimization of signalized intersections for improved multimodal safety and operations. Accommodating pedestrian traffic at intersections is challenging because the demands of multimodal service compete fiercely on limited green time resources. The Highway Capacity Manual prescribes that the parallel vehicle green must exceed “Walk” plus pedestrian clearance interval (PCI) timed by a design walking speed. This static PCI timing is unsafe because seniors and children are likely to be slower than the design pedestrian. Furthermore, a vehicle-flow issue arises when the prolonged PCI exceeds the operationally efficient parallel green: additional vehicle right-of-way, unnecessary for operational efficiency, preempts green time from conflicting phase(s) and increases intersectionwide queuing delays. Queuing delays necessitate a trade-off between competing multifaceted traveler needs. Fuzzy logic control (FLC) proves effective, flexible, and robust in handling competing objectives. With the dynamic PCI concept, this research developed an intelligent traffic signal system that performed friendly pedestrian accommodation and also incorporated FLC into fulfilling multifaceted vehicle needs. The potential benefits from the new system optimized with a genetic algorithm were quantified through a comparison with a standard dual-ring, eight-phase, vehicle-actuated controller, conventionally cited as NEMA (National Electrical Manufacturers Association) control. Microsimulation experiments revealed that the current countermeasure, which lowered PCI timing design speed to strengthen crossing safety, was operationally deficient. The existing timing standard cannot offer adequate safety for all pedestrians, and the NEMA system omits multifaceted vehicle needs in control logic. In contrast, the FLC system fully protects all pedestrians through dynamic PCI and smartly serves manifold vehicle needs well. The FLC system outperforms the NEMA control by embodying a reasonable trade-off between competing objectives in the management of an isolated intersection.

Modern roundabouts have become popular in North America during the past decade. This popularity can be attributed to their great success in Europe and Australia. There has been significant debate, however, over their accessibility for pedestrians. With almost uninterrupted traffic flows, roundabouts make it difficult for the visually impaired to determine safe gaps, as they rely on auditory cues alone. Such crossing is particularly complicated by ambient noises and circulating vehicles on busy urban roundabouts. Various pedestrian signals have been installed at roundabouts overseas. The United States Access Board published a draft guideline proposing pedestrian signals at all roundabout crossings to ensure access for the visually impaired. Roundabout operations can be a complex process of transporting multimodal travelers. There is increased interest in harnessing artificial intelligence to address issues to improve transportation systems. This research developed a crosswalk signal and introduced fuzzy logic control (FLC) into the signal timing to accommodate roundabout users. The system was assessed against the Pedestrian User-Friendly Intelligent (PUFFIN) crossings under varied geometries under different traffic conditions. The objective was to identify potential treatments for improving roundabout accessibility, safety, and efficiency. The results reveal that “distant” layout reduces vehicle delays and queue lengths when the FLC signal is applied, especially under saturated traffic conditions. From safety and operational perspectives, the FLC signal outperforms PUFFIN. The FLC signal implements the signal timing effectively, decreases pedestrian delay, and maintains adequate vehicle circulation. Multimodal traveler needs at a modern roundabout are satisfied in manifold ways.