Evaluation of the Impact of Presence Lighting and Digital Speed Limit Trailers on Interstate Speeds in Indiana Work Zones

Work zone safety continues to be one of the important focus areas for transportation agencies. Previous studies have identified that vehicle speed and lighting conditions are significant risk factors impacting work zone safety. This study evaluated the impact of the use of presence lighting and digital speed limit trailers on nighttime motorist speeds using commercially available connected vehicle speed data. Geospatial analysis was conducted on over 500,000 connected vehicle records to linear reference nearly 18,000 records from 195 unique trajectories to study section during the study period of 2 days. Results showed that median speeds reduced by 4 to 13 mph from 11PM to 7AM during the deployment of presence lighting and speed limit trailers compared to base conditions. A Kolmogorov-Smirnov (KS) statistical test comparing 105 vehicles traveling through the construction zone with presence lighting and speed limit trailers with a group of 90 vehicles during base condition indicated the speeds during the deployment of presence lighting and speed limit trailers were lower than the base condition. Also, increased compliance with the 55 mph speed limit was observed when the presence lighting and digital speed limit trailers were deployed. However, there were two hours (3AM to 5AM) where speeds increased by 0 - 4 mph, perhaps due to the low volume at that hour. The encouraging results support the further deployment of presence lighting and speed limit trailers in nighttime construction zones for reducing vehicle speeds. Those future deployments should be monitored with connected vehicle speeds to collect additional data to broaden the evaluation of these speed mitigation techniques over a diverse set of construction zone activities.

A STUDY ON THE LOW SPEED SHIP THEORY

Based on Baba's assumption,the linearized free-surface boundary conditions at low speed are discussed in order to demonstrate the differences between Baba's and Dawson's free-surface boundary conditions.By using Fourier integral transfor- mation,a method of computing wave velocity potential ,which satisfies the boundary conditions of free-surface and hull surface,is presented.The solution of is found with the powerful technique of asymptotic expansions.With order comparison method,it is found that the hull surface boundary conditions can be neglected when only the ship wave resistance is concerned.The exact analytical solution of two-dimensional slow ship wave velocity potential is derived by neg- lecting hull effect.The results show that the inhomogeneous effect of free-surface is not negligible in the boundary value problems of slow ship velocity potential.