Safety Edge_SM Design and Construction Guide

SECTION 1: INTRODUCTION

1.1 Introduction

The Safety Edge_SM is a relatively simple but effective solution that can help save lives by allowing drivers who drift off highways to return to the road safely.

During conventional paving processes, the pavement is constructed with vertical or near vertical edges. Instead of a vertical drop-off, the finished Safety Edge_SM forms the edge of the pavement with a slope of approximately 30 degrees. Research has shown this "transition from on-roadway surface to shoulder and back is so smooth it defies assignment of any degree of severity." The Safety Edge_SM provides a strong, durable transition for all vehicles and helps prevents pavement edge raveling.

The recommended practice of bringing the adjacent soil or aggregate material (unpaved shoulder or modified soil) flush with the top of the pavement often requires frequent maintenance. When the vertical edge is exposed due to wear/erosion, it can contribute to drivers losing control of the vehicle when attempting to recover from a roadway departure. The Safety Edge_SM concept is when drop-offs along the pavement edge occur, the edge will not be vertical, but has a shape that will not induce tire scrubbing. By including the Safety Edge_SM detail while paving, this safety countermeasure can be implemented system- wide at little or no cost.

1.2 Purpose of the Guide

The Federal Highway Administration (FHWA) works with States and Industry to accelerate the use of innovative technologies. This Guide supports efforts to implement the Safety Edge_SM technology by providing information and guidance to assist agencies in developing standards and specifications for adopting this treatment as a standard practice on all applicable new and resurfacing pavement projects.

The Guide provides information on the various elements to consider when designing and constructing pavement projects with the Safety Edge_SM. The Guide provides insights and lessons learned on previously constructed projects, highlighting items that may vary from conventional pavement design and construction.

1.3 Scope of the Guide

The information for this Guide draws significantly from experiences obtained from 10 formal construction project evaluations conducted in 2010 and 2011, as well as several ad hoc evaluations. It is expected that significant enhancements in equipment and procedures will be forthcoming as the Safety Edge_SM is implemented into standard practice.

The Guide is grouped into four sections, including this introductory section. Section 2 is focused on general design and construction considerations that are applicable to all pavement types and rehabilitation projects. Sections 3 and 4 identify specific considerations for constructing a Safety Edge_SM for asphalt concrete materials (AC) and Portland cement concrete (PCC) pavements, respectively.