Advancing performance-based highway geometric design

* 公路几何设计的传统方法依赖于主要基于经验数据的标准，这些经验数据将驾驶员/车辆性能与几何特性（标称安全性）联系起来。可接受的性能被认为是通过正确应用技术指南产生的，但仍然是产生物理设计尺寸的过程的间接结果。最近，设计师们开始认识到，设计应该基于实际性能，包括碰撞经验（实质性安全），机动性和成本。基于性能（PB）的几何设计已经零星地应用于使用可靠性分析，价值工程和基于上下文的设计等概念。它还得到了一些最新发展的帮助，最著名的是交互式公路安全设计模型，公路安全手册和路边安全分析程序。这些发展为设计人员提供了比传统方法更好的分析工具。然而，由于两个知识差距，它们一般侧重于单一的业绩计量：（1）有些业绩计量没有得到很好的理解，尚未量化;（2）缺乏同时考虑所有相关业绩计量的综合方法。认识到业绩计量之间的基本相互作用意味着需要更正式和全面的工具，以帮助在实践中更广泛地实施。这一需要已得到研究人员和从业人员的承认。拟议的研究解决了这两种类型的公路设施的需求：正在出现的可行的交叉口类型和农村双车道公路，共享相当大的比例的碰撞在公路网。对于每一个公路设施，拟议研究的目标是首先建立相关性能指标的模型，然后将它们集成到一个多目标决策支持系统中。这项研究将启动前所未有的努力，建立强大的，全面的决策支持系统，直接纳入设计过程本身的相关性能指标，而不是在外部的方式，就像今天的情况。因此，这些系统将保证具有成本效益的解决方案，并将不可避免地产生不同的道路设计，从一个位置到另一个，反映在当地环境，项目目标和相对价值的差异。该研究将促进其他公路设施（如农村多车道公路和信号交叉口）和其他道路使用者（如骑自行车者和行人）的PB设计的持续发展。 开发的决策支持系统将使从业人员能够比较关键的设计权衡，并作出更明智的决定。拟议的研究是及时和创新的，并将有助于加拿大公路设计研究的声誉。

***The conventional approach to highway geometric design relies on adherence to criteria based mainly on empirical data that relate driver/vehicle performance to geometric characteristics (nominal safety). Acceptable performance is presumed to be produced through proper application of the technical guidance, but is nonetheless an indirect outcome of the process, which produces physical design dimensions. Recently, designers have begun to recognize that design should be based on actual performance, including crash experience (substantive safety), mobility, and cost. Performance-based (PB) geometric design has been sporadically applied using such concepts as reliability analysis, value engineering, and context-based design. It has also been aided by several recent developments, most notably Interactive Highway Safety Design Model, Highway Safety Manual, and Roadside Safety Analysis Program. These developments provide designers with better analysis tools than the conventional approach. However, they generally focus on single performance measures because of two knowledge gaps: (1) some performance measures are not well understood and have not been yet quantified and (2) a comprehensive methodology that simultaneously considers all relevant performance measures is lacking. Recognition of the fundamental interactions among performance measures implies the need for more formal and comprehensive tools to aid broader implementation in practice. This need has been recognized by researchers and practitioners. The proposed research addresses this need for two types of highway facilities: roundabouts that are emerging as viable intersection type and rural two-lane highways that share a substantial proportion of crashes in the highway network. For each highway facility, the objective of the proposed research is first to model relevant performance measures and then to integrate them in a multi-objective decision-support system.***This research will initiate unprecedented efforts in building strong, comprehensive decision-support systems that directly incorporate relevant performance measures within the design process itself, rather than in an external manner, as is the case today. As such, these systems would guarantee cost-effective solutions and would inevitably produce roadway designs that differ from one location to another, reflecting differences in local context, project objectives, and relative values. The research will promote continued development of PB design for other highway facilities (eg, rural multi-lane highways and signalized intersections) and for other road users (eg, bicyclist and pedestrians). The developed decision-support systems will enable practitioners to compare key design trade-offs and make better informed decisions. The proposed research is timely and innovative, and  will aid the reputation of Canadian highway design research.**