Reliability Evaluation of Sight Distance on Mountainous Expressway Using 3D Mobile Mapping

On mountainous expressway, the poor terrain condition allowed relatively unfavorable road alignment. It is essential to ensure the available sight distance (ASD) of the road meet required stopping sight distance (SSD) of drivers. Traditional measurement of ASD was conducted in horizontal and vertical respectively based on road geometry design. The outcome of the calculation method can be imprecise when there is a combination of horizontal and vertical alignment. Meanwhile, the roadside landscape and vegetation can also affect the accuracy of the result. Considering the required SSD, it is related to several variables including drivers' reaction time, driving speed and friction coefficient of the pavement. Therefore, 3D mobile mapping equipped with LiDAR sensors was utilized to measure the ASD in drivers' vision in a 3D real space. Reliability method was then applied as an uncertainty evaluation method to evaluate the probability of ASD meet the requirement of SSD. Experimental study was conducted on a mountainous expressway section in ZheJiang Province. ASD was extracted firstly from the LiDAR point cloud in drivers' visual perception. Monte-Carlo simulation was then conducted with the consideration of different weather condition to evaluate the probability of ASD meet the requirement. The results showed that crash on road section with probability of failure more than 10% was 1.5 times higher than those on the other road sections. Furthermore, the probability of failure can also be 2.3 times higher in rainy days, proving the feasibility of the proposed method.