Throughout the past year, a number of newly paved roads in and around London were finished without the traditional center lines dividing traffic. According to a white paper published (PDF) by Transport for London (TfL), removal of center lines on roads where the speed limit is less than 30 miles per hour results in a "statistically significant reduction in vehicle speeds.”

Trials in Norfolk and Wiltshire have also supported the removal of the center line to reduce vehicle speed.

The TfL white paper found that drivers tend to slow their driving by up to 4mph on roads with no center lines. But, since the study was only conducted on smooth, newly-paved roads, the researchers at TfL corrected the data to account for the fact that drivers tend to go slightly faster when they feel confident that the road is in good condition. With such corrections, TfL found that the lack of center lines could theoretically reduce average vehicle speeds by up to 8.6mph.

The white paper’s authors admitted that they did not know for sure the exact cause of the slowing traffic, but they suggested that "center lines and hatching can provide a psychological sense of confidence to drivers that no vehicles will encroach on ‘their’ side of the road.”

"Center line removal introduces an element of uncertainty which is reflected in lower speeds,” the authors suggested.

According to the BBC, Assistant Director of Transport at Norfolk County Council Tracy Jessop said that she’s found that with the removal of center lines, “drivers change their behavior because they no longer feel that they have their own lane, so they tend to be more attentive, more cautious, and that does reduce the speed limit.”

She continued, "It does also reduce their journey time because they all become a little bit more aware of people around them and that has been very helpful also for casualty reduction.”

While Alan Bristow, director of road space management at TfL, told the BBC that there were no plans to remove center lines from all roads with a speed limit below 30mph, there is one issue that municipalities might face if they choose to opt out of center lines on new roads: autonomous driving. While fully-autonomous cars are still being lab-tested, lane keep assist is a feature you can find on high-end cars, where the car processes information from a camera to prevent it from drifting into another lane. Granted, that feature is primarily to be used on faster highways, where removing a divider lane has never been in question.

Still, years down the line, fully autonomous vehicles could need to be able to navigate roads without clear lane markers between the correct lane and oncoming traffic.