Illinois Gov. Pat Quinn will soon have to decide whether to sign or veto legislation passed by the state legislature last month that would raise the speed limit on the interstate from 65 mph to 70 mph.

Quinn has been coy, and he hasn't given observers much of an inkling of what he'll decide. But if he does opt to sign the bill, he won't be alone.

Since March, lawmakers in four states have approved legislation that would boost speed limits on their interstates.

It's part of a broader trend ever since the feds created a national speed limit of 55 mph in 1974 in response to the oil crisis. In subsequent years, the limit was raised, and by 1995, it was repealed entirely, giving states full authority to set their own speed limits. Since then, to varying degrees, every state has raised the speed limit on rural interstates; others have increased it on urban interstates and non-interstate roadways too.

Some experts are attributing the latest push for higher speed limits to Texas, which garnered national headlines last year when it created the highest speed limit in the nation of 85 mph on a 41-mile stretch of toll road between Austin and San Antonio.

Want more transportation news? Click here.

This July, for example, the speed limit on most Ohio interstates will increase from 65 mph to 70 mph as a result of state legislation. State Rep. Bill Patmon, one of the sponsors of that bill, says the move was a natural progression from the state's 2011 decision to raise the speed limit on the Ohio Turnpike.

He says the higher speed limits promote more efficient travel between cities in a big state that doesn't have high-speed rail (Gov. John Kasich famously rejected high-speed rail funding).

"In this day of fast food and instant gratification and a lot of impatience, people were glad to see they'll be able to go just a bit faster and (arrive) just a bit sooner," Patmon says.

Utah's speed limit on big sections of the interstate is set to increase from 75 mph to 80 mph as a result of legislation passed earlier this spring. State. Rep. James Dunnigan, the bill's sponsor, says Utah is a big state with huge swaths of rural, undeveloped spaces where a higher speed limits make sense.

He said it's an issue he's spent more than five years pursuing. Initially, he worked to pass legislation to increase the speed limit on 40 miles of interstate and later 80 miles of interstate so that Utah's Department of Transportation could collect safety data that he hopes would help him make the case for more widespread change.

This session, he presented that data to lawmakers. The transportation department's studies concluded that accident rates weren't impacted by the speed limit hikes. Dunnigan also says there weren't any fatal accidents in any of the areas that have higher speed limits.

"You have to look at the data instead of emotion," Dunnigan says.

The state DOT will ultimately decide which areas get the higher limits and which don't, but Dunnigan believes that about 350 miles of Utah interstates will get the new limits. He says he isn't interested in taking speed limits beyond 80 mph, but he wants to see it on more parts of the interstate. He also says next legislative session, he'll try to increase the speed limit on parts of the interstate in urban areas from 65 mph to 70 mph.

And in Maine, the legislature has approved a move to let the Department of Transportation raise the speed limit on Interstate 295 to 75 mph; it's currently set at 65 mph on most parts of the roadway. A speed limit hike is pending in North Carolina's legislature.

Unsurprisingly, safety advocates say they're troubled by the movement. Higher speeds don't necessarily mean more accidents, but they do mean the accidents that do occur tend to be more severe, says Kara Macek, a spokeswoman for the Governors Highway Safety Association.

"It's a simple matter of physics," she says. "The faster you're going, the worse your injuries will be."

Russ Rader, a spokesman for the Insurance Institute for Highway Safety, says lawmakers have a political motivation to hike speed limits because it plays well with voters. Critics of the heightened speed limits say they're also the result of pressure from the trucking industry.

Rader says the creation and subsequent elimination of the federally imposed speed limit gives researchers a valuable tool for analyzing the impact of higher speed limits. His organization cites a 2009 study that estimates the higher speed limits across the country in the wake of the 1995 repeal led to 12,545 excess deaths.

Yet other research suggests the effect isn't so stark. Purdue University researchers, for example, found the likelihood of fatalities and serious injuries didn't increase when Indiana raised its Interstate speed limit from 65 mph to 70 mph in 2005. Illinois lawmakers cited that research as they made the case for higher speed limits, despite opposition from the Illinois State Police and Department of Transportation.

Craig Neustaedter, a traffic engineering consultant who helps California cities set speed limits, says speed alone is not typically a primary factor that causes collisions. He says when speed limit hikes are considered, governments should conduct an engineering analysis of the roadway and determine whether it's had a history of collisions. If that's done, a speed limit can be increased safely in some areas.

Moreover, he says, freeways -- especially those that are part of the interstate system -- are typically designed to safely accommodate speeds of 80 mph. "A change in the speed limit, in and of itself, if done properly... should not create a hazardous condition," Neustaedter says.