Dept. of Civil & Environmental Eng., The Hong Kong Polytechnic University, Hong Kong.
Lyles School of Civil Eng., Purdue University, W. Lafayette, IN, USA; Robotics Institute, School of Computer Science, Carnegie Mellon University, Pittsburgh, PA, USA.
J Safety Res. 2020 Dec;75:222-232. doi: 10.1016/j.jsr.2020.09.014. Epub 2020 Nov 6.
Walkability continues to attract great attention from urban planners, designers, and engineers as they recognize not only the merits of pedestrian facilities in terms of the health benefits but also their demerits in terms of accident risk to pedestrians. Wide footpaths improve the pedestrian environment and experience, and thereby motivate travelers to walk as much as possible. However, if footpaths are too wide, they may leave a smaller space for the roadway. On the other hand, wide road lanes may lead to higher road vehicle safety but are costly to construct and maintain and also may leave little space for the footpath. Evidently, for a fixed urban space, what is needed is an optimal balance between the vehicle lane and pedestrian path. This problem is encountered routinely in dense cities including Hong Kong where land availability is severely limited.
To address the issue, this paper first establishes safety performance functions (SPFs) for the pedestrian space and the road space, using the random-parameter negative binomial regression. The results indicate the extent to which road lane and footpath width changes are associated with changes in in-vehicle occupant and pedestrian casualties. Then the paper uses the SPFs to develop a methodology for optimizing the width allocations to the road lanes and footpaths, duly considering the user (safety) costs and agency (construction) costs associated with each candidate allocation of the widths. Finally, the paper analyzes the sensitivity of the optimal solution to the relative weights of user cost and agency cost.
When user and agency costs are considered equally important, the optimal lane width is 5.4 m.
It is observed that the road space allocation ratio used by the Hong Kong road agency suggests that the agency places a higher weight to user cost compared to agency cost. Practical Application: The findings can help incorporate design-safety relationships, and the stakeholders (agency and users) perspectives in urban road and footpath design.
步行的便利性继续吸引着城市规划者、设计师和工程师的关注，因为他们不仅认识到行人设施在健康效益方面的优点，也认识到它们在行人事故风险方面的缺点。宽阔的人行道改善了行人环境和体验，从而促使行人尽可能多地步行。然而，如果人行道太宽，可能会为车道留下更小的空间。另一方面，宽阔的车道可能会提高道路车辆的安全性，但建设和维护成本高昂，也可能为人行道留下很少的空间。显然，对于一个固定的城市空间，需要在车道和人行道之间实现最佳平衡。这个问题在包括香港在内的人口密集城市中经常遇到，因为这些城市的土地供应非常有限。
为了解决这个问题，本文首先使用随机参数负二项回归方法为行人空间和道路空间建立安全性能函数 (SPF)。结果表明，车道和人行道宽度的变化与车内乘客和行人伤亡的变化有多大关系。然后，本文使用 SPF 开发了一种优化道路车道和人行道宽度分配的方法，充分考虑了与每个候选宽度分配相关的用户（安全）成本和机构（建设）成本。最后，本文分析了最优解决方案对用户成本和机构成本相对权重的敏感性。
当用户成本和机构成本同等重要时，最优车道宽度为 5.4 米。
观察到香港道路机构使用的道路空间分配比例表明，机构相对于机构成本更重视用户成本。
研究结果可以帮助将设计安全关系以及利益相关者（机构和用户）的观点纳入城市道路和人行道设计中。
