This work seeks to assess the impact of adding a lane for slower trucks on a divided multilane highway on CO 2 emissions. A portion of the U.S. 101 highway in San Luis Obispo County in California consists of the Cuesta Grade which is a 2.75-mile segment with a 7% grade. A microsimulation software, VISSIM, was used in conjunction with the Environmental Protection Agency's emissions model, MOVES, to estimate CO 2 emissions on the corridor before and after the construction of the third lane. It was found that CO 2 emissions decreased between 1998 (before) and 2012 (after the 2003 lane addition), but the effect of the truck lane was shown to be different for the northbound (uphill) and southbound (downhill) directions. The truck lane in the northbound direction exhibited a 9.5% decrease in volume with 10.7% decrease in emissions, and the southbound direction experienced a 20.3% increase in volume but 7.4% decrease in emissions. For the northbound (uphill) direction, emissions seemed to correlate more closely with traffic volumes while a sensitivity analysis revealed travel speeds had a more profound effect on southbound (downhill) emission rates. In the conclusion section, ideas to further validate the emissions estimate are discussed. Emissions seemed to correlate more closely with traffic volumes (uphill) while travel speeds had a more profound effect on southbound (downhill) emission rates. One factor to be accounted for is the change in volume which seems to play a much larger role in emissions than roadway features or topography.

The right-turn flashing yellow arrow (FYA) signal display is still considered a new signal practice in the United States. The Manual on Uniform Traffic Control Devices (MUTCD; 2009) allocates a signal phasing section for the right-turn FYA, which requires a four-section configuration. It supports multiple phase indications that guide the motorists through permissive, protected, or permissive or protected phases. However, there are no right-turn FYA or protected permissive right turn (PPRT) guidelines in place with a focus on operational efficiency. In this paper, we investigated two permissive right-turn FYA phases in various traffic conditions and signal timing plans. The first permissive right-turn FYA phase is the right turn on impeding through (RTOIT) taking place during cross-street through movement. The second permissive right-turn FYA phase occurs during opposing left-turn movement and is thus called right turn on impeding left (RTOIL). We aimed to develop warrants leading to the efficient implementation of permissive right-turn FYA phases based on a micro-simulation analysis. The response, the average maximum right-turn throughput (MRTT) per cycle, was categorized into three categorical variables represented as the nonefficient (NE), low efficient (LE), and efficient (E) categories depending on the number of executed right turns per cycle. A multinomial logit model was developed to establish a decision support system that predicts the efficiency attributes of the permissive RTOIT and RTOIL FYA phases that can help traffic management center operators in planning and operational-level applications.

This research investigates the characteristics and contributing causes of pedestrian crashes that occurred in Central Florida over a 5 year-period at intersections and mid-block crossings along roadway segments. The factors contributing to pedestrian crashes were classified into four main categories: location characteristics, pedestrian factors, driver/vehicle characteristics, and environmental-related factors along with their corresponding crash characteristics. Categorical Principal Components Analysis (CATPCA) was applied to understand the structure of a set of variables and to reduce the dimen-sionality of the dataset to a predefined number of dimensions and components. CATPCA analysis revealed that four dimensions accounted for almost 50% of the model indicating strong positive relationships between datasets with driver and pedestrian characteristics along with their corresponding crash characteristics relatively significant than the location and the environmental characteristics. The analysis showed that majority of the intersection crashes were during nighttime with pedestrians under influence and failing to yield to the right of way (ROW). They included mainly left-turn and right-turn crashes. In addition, drivers were also found at fault due to vision issues resulting from absence of lighting at intersections and categorized as failure to yield to the ROW. At midblock locations, major crash types were through moving vehicles hitting pedestrians crossing and walking along the roadway especially during nighttime conditions. However, majority of the crashes were at locations away from the designated crossings likely due to the long distances between legal crossing locations and pedestrian's failure to utilize them. The findings of this research and examining the factors affecting pedes-trians' crash likelihood and injury severity can lead to better crash mitigation strategies, countermeasures and policies that would alleviate this growing problem in Central Florida.

Since their introduction in the late 1990s, basic turbo roundabouts have made a great success in several European countries. Researchers, however, have been unable to reach a general consensus on the operational performance advantages and benefits derived from such a novel design of multi-lane roundabouts, as compared with conventional double-lane roundabouts. Those contradictory results could be mostly attributed to wide variations in driver behavior among different traffic environments. This study aims to analyze and evaluate the operational performance of an existing, congested double-lane roundabout in the State of Florida and a proposed, simulated basic turbo roundabout. Local field data was used to accurately calibrate and validate the microsimulation models and to precisely capture local driving behavior. Three scenarios were created for evaluation. Results indicated that basic turbo roundabouts with regulatory entry speed as per Dutch standards, that is, 25 mph, were the most suitable alternative to reduce average delay and provide comparable capacity to double-lane conventional roundabouts for traffic flow ranging between 4,350 and 6,050 vehicles per hour. However, double-lane conventional roundabouts, including their major and minor approaches, always managed to process significantly more vehicles.

With the growing number of vehicles utilizing roads in the city of Doha, Qatar, most intersections, particularly multilane roundabouts, have been facing traffic congestion dilemma, where traffic demand exceeds capacity. A new design for multilane roundabouts, known as a rotor turbo roundabout, was considered as an alternative to an existing highly congested multilane roundabout. The new design features spiral roadway markings and raised lane dividers which prevent maneuvering within the roundabout and eliminate cutting-offs and weavings. This design has achieved high capacity and low delay in many European countries. In this study, a traffic simulation program, VISSIM, is used to model the complex traffic operation of both the existing and proposed multilane roundabouts and to replicate the high traffic conditions and aggressive driving behavior prevalent among the Middle East countries. Three different rotor designs were examined in an attempt to have a valid comparison between the two types of roundabouts and to adhere to the standard design of the rotor roundabout without violating its essential features. The proposed designs performed slightly better on the minor approaches and managed to deliver an overall improved LOS compared to the conventional design. Major approaches, however, exhibited an increase in vehicle delay and queue lengths. The results showed that the capacity of the conventional three-lane roundabout was always superior to the capacity of the rotor roundabouts. It was concluded that rotor roundabouts may not be suitable for intersections with high demand volumes exceeding 4500 vehicles per hour, and whenever the traffic flow condition is oversaturated.