Can't Drive 65? How Fast Should The National Speed Limit Really Be?

Left to their own devices, American drivers confronted with an open stretch of interstate highway tend to drive at about 70 miles per hour—whatever the legal speed limit happens to be.

That's the finding of an analysis of speed data gathered by TomTom Inc., a marketer of GPS navigation devices. This helps to explain why safety advocates and conservationists are losing the long-running debate over lowering freeway speed limits.

The Virginia legislature last week passed legislation raising the speed limit on rural interstate highways to 70 mph from 65 mph. The state's new Republican governor, Bob McDonnell, put boosting the legal speed limit high on his list of priorities, and got action less than three months after taking office.