The factors affecting the acceptance of Autonomous Vehicles (AVs) in Saudi Arabia were examined by conducting a stated choice survey among 500 participants. Descriptive analysis showed that the participants believed that using AVs will decrease the risk of car crashes and help them safely reach their destination. Parametric analysis and prediction models showed a wide variation in public opinion regarding willingness to use AVs, despite an average high score on this factor. The study found that the trust in AVs was low, and women favored AVs more than men. Prediction models showed that age, trust, and being tech-savvy determine the willingness to use AVs. As younger participants had a high willingness to use AVs, we recommended focusing on changing the perception of older drivers to increase overall AV acceptance by increasing their trust in this new technology and highlighting the features of AVs. From the findings of this study, it is expected that wide-scale adoption of AV depends upon its competitiveness with the traditional and its performance in terms of enhancing road safety.

Analysis of travel mode choice is vital in policymaking and transportation planning to comprehend and forecast travel demands. Universities resemble major trip attraction hubs, with many students and faculty members living on campus or nearby. This study aims to investigate the effects of socioeconomic characteristics on the travel mode choice of university students. A nested ensemble approach with artificial neural networks (ANNs) was used to model the mode choice behavior. It was found that students generally prefer motorized modes (bus and car). A more detailed analysis revealed that teenage students (aged 17–19 years) had an approximately equal probability of selecting motorized and non-motorized modes. Graduate students revealed a higher tendency to select motorized modes compared with other students. The findings of this study demonstrate the need to promote non-motorized modes of transport among students, which is possible by providing favorable infrastructure for these modes.

Roundabouts are common alternatives to stop- and signal-controlled intersections and have grown in popularity in response to the promise to reduce traffic crash severity at intersections. In Wisconsin, more than 300 roundabouts have been installed. Studies of these intersections have found a 38% reduction in fatal and injury crashes. However, a 12% overall increase also was found, and this finding is not unique to Wisconsin. An increase in less-serious crashes can lead to a negative public perception about roundabout benefits. The causes of rear-end collisions (a common type of low-severity crash) were examined. Four years of crash reports from 55 roundabouts were analyzed along with the geometric conditions of the roundabouts. The 16- to 24-year-old driver age group represented a significantly higher proportion of involvement in rear-end collisions than in total crashes across the state. Negative binomial models were created for roundabout approaches. For combined one-lane and multilane roundabout approaches, annual average daily traffic, sawtooth pavement markings, and high deflection angles were significantly correlated with an increase in the expected number of rear-end collisions, and wider entry was significantly correlated with a decrease in the expected number of rear-end collisions. For one-lane approaches, “Yield” pavement markings led to an expected reduction in crashes, as did the presence of horizontal curves within 250 feet of a roundabout. These findings reflect the complexity of driving at roundabout approaches, especially for younger drivers. Results also indicate the importance of proper pavement markings at approaches.

Truck platooning is a truck operation system in which one or more trucks closely follow a lead truck. The system is advantageous for road freight and promises to contribute to developing the next generation of road transportation due to its many benefits, including reduced fuel consumption and emissions and improved traffic flow. However, truck platooning also has some potential disadvantages, such as the occlusion of post-mounted road signs. In this study, a VisSim simulation model was used to evaluate truck platooning’s impact on road sign occlusion on four-lane and six-lane freeways. A regression model was then used to investigate road signs’ occlusion by conventional trucks and platooned trucks. The regression model found that sign occlusion increases with increasing the number of lanes on the highway, headway within a truck platoon, traffic demand ($\mathrm{veh}/\mathrm{h}/\ln$ ), truck percentage, and platooning penetration (%). Conversely, a higher number of trucks in a platoon (platoon length) decreases sign occlusion because it reduces the overall number of truck platoons, including individual trucks. A 100% truck platoon penetration particularly caused sign occlusion for up to 82.3% of other vehicles under certain conditions. This study’s findings demonstrate the need for transportation agencies to include countermeasures for mitigating sign occlusion before deploying truck platooning.

Research has shown that elongated pavement marking letters and arrows significantly improve recognition distance; however, the effect of elongated pavement marking signs, which are symbolized pavement markings that are elongated versions of signs, has not been evaluated. The goal was to evaluate the effectiveness of elongated pavement marking signs in conjunction with the post-mounted signs they complement. Results from a driving simulator evaluation indicate that recognition distance increases quadratically as elongation ratio (i.e., the ratio of height to width) increases. Considering the trade-off between cost and recognition distance, an elongation ratio of 5:1 was chosen for field evaluation of speed limit regulatory signs and curve warning signs. A before-and-after study was conducted at sites in Kansas, Missouri, and Wisconsin. Operating speeds of free-flow vehicles were used as the measure of effectiveness; speed data were collected upstream of, at, and downstream of the corresponding post-mounted sign. The speed limit sign was tested at four sites (at least one in each state) and was found to reduce operating speeds effectively at three of the four sites. A curve warning sign was tested at three sites (two in Kansas, one in Wisconsin), and operating speed reductions were observed at two of the sites. Field data results indicated that the evaluated regulatory and warning elongated pavement marking signs reduced vehicle speeds. This demonstrates they can be effective in reinforcing a warning or a regulatory message to drivers. Future research should evaluate durability and long-term effectiveness and should test other signs.