SAFETYLIT WEEKLY UPDATE

We compile citations and summaries of about 400 new articles every week.
RSS Feed

HELP: Tutorials | FAQ
CONTACT US: Contact info

Search Results

Journal Article

Citation

Hawkins J. J. Transp. Eng. 2007; 133(4): 223-231.

Affiliation

Zachry Dept. of Civil Engineering, Texas A and M Univ., College Station, TX 77843-3136, United States

Copyright

(Copyright © 2007, American Society of Civil Engineers)

DOI

10.1061/(ASCE)0733-947X(2007)133:4(223)

PMID

unavailable

Abstract

For over 50 years, the basis for calculating the length of sag vertical curves has been the sight distance based on a 1 degree upward divergence of the headlamp beam. Over the last 20 years, headlamps have transitioned from being 100% sealed beam to modern replaceable bulb headlamps that project less light above the horizontal plane compared to the sealed beam headlamps that are the basis for the sag curve design. This paper analyzes the performance of modern headlamps with respect to sag vertical curve design by calculating the amount of illumination reaching the pavement in a sag curve. The analysis indicates that the headlamp beam angle used to calculate sag curve length should change from 1 to 0.75 degrees to provide an illuminance level with modern headlamps that is equal to the illuminance provided by sealed beam headlamps. Such a change would increase the K values for sag curve design from 13, 30, and 55 to 15, 37, and 70 for design speeds of 110, 80, and 50km/h, respectively.

NEW SEARCH


All SafetyLit records are available for automatic download to Zotero & Mendeley
Print