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CHAPTER 1 Introduction Purpose and Scope of the Guide This document contains guidelines for the geometric design of driveways. The guidelines are an outgrowth of a literature review and synthesis, a survey of state DOTS, and field studies that were a part of NCHRP Project 15-35, "Geometric Design of Driveways." This publication com- plements documents such as the AASHTO Policy on the Geometric Design of Streets and High- ways (1-1) and the Access Management Manual (1-2). This guide is intended for use in both the public and private sectors. The following driveway design objectives guided the authors during the preparation of this guide: Provide a safe environment for various users: bicyclists, motorists, and pedestrians (includ- ing pedestrians with disabilities and transit passengers). Provide geometry that accommodates the characteristics and limitations of the various users, and avoid geometric conditions that create traffic operations problems. Provide driveways that allow traffic to flow smoothly. Avoid driveway locations that create traffic operations problems. Provide driveways that are conspicuous and clearly delineated for the various users. Although it may be impossible to perfectly achieve these objectives, some designs come much closer than others in achieving these objectives. Every driveway connection creates an intersection, which creates conflicts with bicyclists, pedestrians, and other motor vehicles. An objective of good design is to seek a balance that minimizes the actual conflicts and accommodates the demands for travel and access. Driveways can be defined as private roads that provide access between public ways and activ- ities or buildings on abutting land (1-3). However, when roadway designers use the term "drive- way," they are often referring to just a part of a driveway--the area where the driveway intersects the public highway or street. With few exceptions, the contents of this guide reflect the roadway designer definition of driveway and do not address the design of a driveway well within a private site, except as such design affects the driveway intersection with the public roadway. Many of these recommendations were prepared to address access connections that are designed to look more like the typical driveway rather than those looking like public roadways. Need for This Guide Driveways are integral to the roadway-based transportation system. They are found along most roadways throughout urban, suburban, and rural areas. They range from single-lane connections serving single-family residences to multilane, divided-access connections to major activity centers. 1