چكيده به لاتين
Regardless of the properties of links and junctions, road network structure and their arrangement effects on traffic safety and this is a topic that has been less discussed in the area of traffic safety. In this study by defining a quantitative indices of street network pattern, its impact on the risk of traffic accidents has been observed in 178 Mashhad's Traffic Analysis Zones (TAZs). For this purpose, with using Mashhad's crash data of 2008-2010 years, the Space Syntax measures such as Integration, Connectivity, Choice, Entropy, Intelligibility and other descriptive variables such as average car ownership, vehicle kilometer traveled(VKT), number of junctions and road network density, The Bayesian accident prediction models were fitted to data. Poisson Log-Normal model was developed to investigate and compare the ability of Space Syntax measures in improving crash prediction models and the BYM model with Conditional Autoregressive (CAR) prior was used to incorporate the spatial correlation of nearby zones. Finally the risk of traffic accidents was estimated using the selected final model. The results showed that applying the descriptive variables of the road network pattern leads to the improvement of crash prediction models. The performance of the Connectivity measure was better than other quantitative variables of the road network pattern and considering the spatial correlation of the TAZs improved the model's fit to data. The results showed that the final selected model is able to predict 86.4% of the risk of accidents in Mashhad's TAZs. The results indicate that the Integration (mean = 0.3174; 95% CI = [0.2393, 0.3954]), Connectivity (mean = 0.338; 95% CI = [0.2664, 0.4109]) and Intelligibility (mean = 0.2839; 95% CI = [0.1983, 0.3694]) measures are directly related to the risk of accidents while Entropy (mean = −0.2239; 95% CI = [−0.3131, −0.1351]) and Choice (mean = −0.184; 95% CI = [−0.2791, −0.09008]) are inversely related. This means that by changing the road network pattern from Irregular to Grid, traffic safety is decreased. This achievement can be used to design a new road network with more safe design of network pattern.
