Speed Characteristics and Safety Risk Level Evaluation for Nighttime Roadway Work Area

More and more roadway projects are conducted during nighttime to satisfy heavy travelling demands in the daytime. However, the Nighttime Roadway Work (NRW) produces several safety problems. As a developing region of China, these problems expose later than some developed countries, and there is scarcely any valid crash samples for NRW safety analysis. Therefore, a surrogate safety assessment philosophy is adopted in the paper. Firstly, the field survey and statistical analysis approaches are adopted to acquire percentile speed characteristics of vehicles passing through work-zones during nighttime. Secondly, a kind of safety risk evaluation model is established to assess NRW safety levels. The results reveal that 1) speeding problems severely exist in the NRW zone and safety risk levels are comparatively high; 2) from speed characteristics of NRW in a city expressway by lanes, speeding ratio in the activity area is higher than 90% and in the lane in transition area the ratio is higher than 30%; 3) from speed characteristics of NRW in a city expressway by vehicle types, speeding ratios of all type vehicles in the activity and transition area are higher than 90% and 30% respectively; 4) the speeding ratio in freeway NRW area is close to 100%; 5) the safety risk analysis indicates that risk levels of lanes in transition area are comparatively high, and also the safety risk level of large vehicles is higher compared to other type vehicles. Finally, several useful tips for the prevention of speeding in the NRW area are suggested.