Iowa parents are putting their teen drivers in danger – in writing. According to a study by the Iowa Department of Transportation, a majority of Iowa parents signed waivers that exempted their teen drivers from passenger restrictions under Iowa’s Graduated Driver License (GDL) law.

In 2013, the Iowa legislature passed a law that restricted the number of passengers a teen driver can carry to one unrelated passenger for the first six months after receiving their intermediate license. This is a common GDL law that has been passed in many states. In some states, teen drivers can’t carry any passengers other than a sibling for the first six months.

GDL laws were passed in an effort to allow more time for a teen to gain more driving experience without distractions. The reason for the passenger restrictions is that, the more teen passengers a teen driver carries, the more distracting the driving situation is. According to the Governors Highway Safety Association, adding just one passenger increases a teen driver’s crash risk by 50 percent. Put three or more passengers in the car, and that “risk is nearly four times greater.

The Insurance Institute for Highway Safety says that Iowa could cut its fatal teen crash rate by more than half if tougher teen driving laws were enacted.

For some reason, when the Iowa legislature passed this law, they included a provision that allowed parents to sign a waiver that exempted their teen from the passenger restriction provision. This appears to be a popular provision because 90 percent of parents of teen first time drivers have signed the waiver.

If parents were educated on just how dangerous teen passengers of teen drivers can be, they might reconsider and revoke the waiver. Even without such a law, parents should limit the number of passengers their teen driver can carry until the teen driver has six months to a year of driving experience.

Read more: Majority of Iowa parents waive teen driving restriction