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Do cell phone laws make the roads any safer?

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Every state legislature has considered regulations that would prohibit the use of cell phones while driving. Several have enacted laws that prohibit drivers from using hand-held cell phones but allow drivers to use hands-free devices. Will these laws make the roads any safer?

In January of 2010, the Highway Loss Data Institute issued a report that concluded that the crash risk did not diminish when hand-held cell phone bans went into effect. So it would appear that laws banning hand-held phones do not make the roads any safer. Should we be surprised by this conclusion?

No. Here's why.

First, epidemiology studies that have examined the crash risk have found that the odds of a crash are the same for hand-held phones and for hands-free phones. For example, an article published in 1997 in the New England Journal of Medicine established that the odds of crashing were 4 times higher when the driver was using a cell phone and that the crash risk was the same for hand-held and hands-free units. This finding was replicated in an article published in the British Medical Journal in 2005.

So, the data indicate that hands-free cell phones are not any safer than hand-held cell phones. If drivers comply with the law and purchase a hands-free kit, there is no reason to expect crash risk to diminish. In both cases, the odds of a crash are 4 times higher than if the driver was not using a phone (incidentally, this is the same crash risk that we see with drivers who are intoxicated at the legal limit).

Second, laws are effective if they are enforced. When a ban goes into effect, enforcement (and compliance) tends to be high initially but slowly diminishes over the subsequent months and years. Cell phone restrictions are also much more effective if the violation is a primary offense (meaning that you can be pulled over just for using the cell phone while driving) than if the violation is a secondary offense (meaning that you cannot be pulled over just for using a phone while driving). For cell phone restrictions to have any teeth, they need to be primary offense laws that are well enforced by police.

Finally, it is not known if hand-held restrictions will change the pattern of usage. With no enforcement, then there is little reason to expect a change in behavior. If drivers reduce their usage (perhaps because they do not have a hands-free kit or possibly because they learn about the cognitive distractions associated with cell phone use), then there may be some safety benefit to the laws. However, if drivers make the incorrect assumption that hands-free cell phones are safer and talk more than they would have had they used a hand-held phone, then the impact of a hand-held ban could be counterproductive.

For cell phone restrictions to make the roads safer, they need to prohibit both hand-held and hands-free devices.

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