A study by two University of California, Berkeley, graduate students has found no correlation between cell phone use during weekday evening driving and car crashes.

Published by the American Enterprise Institute for Regulatory Studies, the study conflicts with the conclusions of more than 125 earlier studies, which generally found that cell phone usage tended to increase the incidence of accidents.

The UC Berkeley study was published before the recent deaths of five upstate New York girls, who were killed when the SUV they were riding in smashed directly into a tractor-trailer. The driver's phone was in use text messaging immediately before the crash, investigators said.

The UC Berkeley study was developed by Saurabh Bhargave and Vikram Pathania, who noted that their conclusion was contrary to the bulk of earlier cell phone usage studies. "The most notable of the over 125 studies has concluded that cell phones produce a four-fold increase in relative crash risk -- comparable to that produced by illicit levels of alcohol," they said in their report. "In response, policy makers in fourteen states have either partially or fully restricted driver cell phone use."

Noting that cell phone calls generally increase after 9 p.m. -- often when "free" calling begins -- the authors expected the number of motor vehicle crashes to increase after 9 p.m., too. That wasn't the case, however, as the graduate student economists discovered the crash rate remained flat -- and sometimes was lower. "We were quite shocked," said Bhargava.

Their results generally tracked the traditional evening crash rate in which crashes tend to decline on weekday evenings whether cell phones are used or not. "We find no evidence for a rise in crashes after 9 p.m. on weekdays from 2002-2005," they said. "It is important to note, however, that this research does not imply that cell phone use is innocuous. It simply implies that current cellular use by drivers does not appear to cause a rise in crashes. It could be that drivers who use such devices compensate for the added distraction by driving more carefully."

The Insurance Information Institute cites two potentially dangerous practices often used by cell phone users in cars. First, dialing a number while driving can be dangerous. The institute also said drivers can become so absorbed in their cell phone conversations that they can be distracted from attentive driving.