If you hear a radio traffic reporter in Houston say that a portion of the freeway is closed because of an "accident investigation," it usually means there's been a fatality. Drivers can expect lengthy backups for at least the next couple of hours as busy roadways grind to a sudden halt. They'll then have to detour onto feeder roads and neighborhood streets. But what, exactly, are the police doing?
Houston Assistant Police Chief John Trevino says on any given weekend there's at least one freeway shutdown, and it's usually the result of an accident caused by a drunk driver. Houston bars close at 2:00 AM and a wreck shortly thereafter can keep a roadway closed until well after sunrise. Police have to gather evidence for felony cases as serious as intoxication manslaughter. In Texas that offense could get someone up to ten years in prison.
Trevino says when there's been a fatality, the police department sends a team of six accident investigators. They take photos, measure skid marks, and examine debris patterns. Not wanting to cause another accident, police set up two separate barricades to ensure investigators' safety as traffic is detoured off the freeway. A prosecutor from the district attorney's office also reports to the scene, and Trevino says that can also add to the closure time if there's a delay in getting someone there.
If the wreck involves an eighteen-wheeler or a fuel spill, the shutdown could last even longer. Trevino says if there's damage to a bridge or overpass, a crew from the Texas Department of Transportation has to make an assessment before the road can reopen.
And, like any crime scene, it's crucial to gather evidence quickly. Troy Walden with the Texas Transportation Institute says if cars were allowed to pass while police did their investigation, it would be much more difficult to figure out what happened.
"For instance you have short-lived evidence such as your skid marks and debris patterns such as glass patterns that are spread across the roadway surfaces, fluid transfer. And all those things are very short-lived evidence. And in order to be able to capture that, we have to shut it down so that other cars don't run through and disrupt the patterns and eradicate a lot of the evidence."
Houston police say if there's a high-profile accident they may have to shut down the freeway a second time for additional investigation, but they try to do it at a time when there's the least inconvenience to drivers.