Understanding the marginal impacts of park-and-ride (P&R) transit facilities can help in planning an efficient transit system. However, these marginal impacts are not well established in a U.S. context. This study helps to fill this gap using a survey of P&R users from the Twin Cities region in which the questions were specifically designed to determine how respondents would react to the removal of a P&R facility. The responses allow for an estimation of the net (or marginal) impact on ridership and vehicle miles traveled (VMT) directly attributable to the presence of P&R facilities. Over 80% of the surveyed P&R users would only use transit if they had access to a P&R facility. They would generate an average of 19 additional VMT per round trip without a P&R option. If access to their current P&R facility was removed but they were given the option to choose an alternative facility, the respondents who would quit using transit dropped to 32% with an average of 10 additional VMT generated, although these numbers vary to some degree when broken down by specific P&R facilities.

了解停放式（P＆R）运输工具的边际影响可以帮助规划有效的运输系统。但是，在美国背景下，这些边际影响尚不充分。这项研究通过对双子城地区的P＆R用户进行调查，帮助填补了这一空白，在该调查中，问题是专门为确定受访者对P＆R设施拆除后的反应而设计的。这些响应可以估算出直接由于P＆R设施的存在而对乘车和行进的车辆行驶里程（VMT）的净（或边际）影响。超过80％的受访P＆R用户只有在使用P＆R设施时才会使用公交。如果不使用P＆R选项，他们每次往返平均将产生19个额外的VMT。如果可以访问其当前的P＆