@article{ref1,
title="Philadelphia's new program for traffic signal modernization",
journal="Traffic quarterly",
year="1956",
author="Butterfield, S.f.",
volume="10",
number="2",
pages="268-284",
abstract="Philadelphia has recently begun a major revitalization of its antiquated traffic signal system. Philadelphia's first traffic signal was installed in 1923 at an outlying location on Frankford Avenue, then one of the city's major traffic arteries. This article describes Philadelphia's experience and trials during the traffic signal modernization program which might perhaps provide assistance to other major metropolitan areas confronted with similar problems.<p />",
language="",
issn="0041-0713",
doi="",
url="http://dx.doi.org/"
}