Operational and Safety Impact Analysis of Implementing Emergency Shoulder Use (ESU) for Hurricane Evacuation

The emergency shoulder use (ESU) was implemented in Florida in September 2017 to facilitate mass evacuation before Hurricane Irma made landfall on the shores of Florida. ESU was implemented on the northbound I-75 for about 39 h and eastbound I-4 for about 6 h when the left shoulders were opened for use as travel lanes. This study discusses the operational and safety effects of ESU. The operational effects of ESU were studied and compared with other alternatives including one-way operation (contraflow) and both left and right shoulder use. The findings showed the left shoulder ESU could be an effective alternative to one-way operation. The one-way operation was not a preferred method as it can only be operated during the day time, requires massive resource allocation, and hampers emergency services reaching to different parts of the state. However, ESU on the left shoulder offers minimal disturbance to traffic and is easy to deploy. The safety impact analysis was performed by conducting a descriptive statistical comparison of crash types, severity, and other relevant factors during ESU operations. The crash analysis showed that the observed number of crashes on an urban I-75 segment during ESU operation is commensurate with normal operation with saturated traffic conditions, in contrast a rural segment experienced a higher observed crash rate than the predicted rate with saturated traffic conditions. The predictive analysis of ESU crashes also showed that ESU implementation helped to reduce the expected number of crashes significantly.

Benefits and Risks of Truck Platooning on Freeway Operations Near Entrance Ramp

Truck platooning attracts considerable attention thanks to the promising fuel consumption benefits and business model. Nevertheless, concerns over the influence of long truck platoons on other traffic are raised by road operators. It is intriguing to understand under what conditions truck platooning will influence other traffic and what are the magnitudes of the influence. To this end, this paper reports a simulation study on examining the effects of truck platooning on freeway operations near an on-ramp. Systematic experiments were conducted with varying demand, market penetration rates (MPRs), intra-platooning gap, and platoon size. Moreover, three alternative strategies for truck platooning to accommodate merging traffic were tested: allowing courtesy lane change of trucks, active yielding, and keeping a larger intra-platoon gap than the acceptable gap for human drivers to change lane. Simulation results show that at high MPRs of truck platooning, the system mitigates congestion and increases throughput, at the expense of merging failures. The merge location distributions shift toward the end of the acceleration lane at congested flow and high MPRs. The effect on average merging speed is insignificant, but the merging speed in saturated traffic with truck platooning shows larger variability. At free flow and low MPRs, the influence is insignificant. Evaluation of the three alternatives concludes that the yielding strategy is most effective in resolving the merging problem with truck platooning. Courtesy lane change is not always possible because of the high speed difference between lanes and keeping a larger time gap suppresses the benefits in congestion mitigation and throughput increase.

MASA MENUNGGU KERANA MASA LENGAH BAS DI PUTRAJAYA

Passenger waiting time is included in the estimated travel time. Waiting time will be unstable and unpredictable in estimation because of inconsistencies of bus arrival times at stops. These can result an unreliable of bus service. This paper examines the waiting time due to three factors; delay resulting from inaccuracies of bus departure time, delay during the process of boarding and alighting passengers and delay when the bus unable to maintain constant velocity because of saturated traffic flow. The research used the combination of mathematical model and Design Expert Research Methodology Surface (RSM) applications which has pivotal role in acquire optimum waiting time based on constraints delay between two arrival times at stop. The optimum waiting time obtained from the output design target in range 0-15 minutes were 4 minutes for route L01 and 5.87 minutes for L05. The estimated waiting time obtained from this research can be used as a key feature in the design of buses operating to minimize the delay and at the same time get the reliability of passengers.