NASCAR's Vice President of Competition, Robin Pemberton, informed teams of a new rule for this season, which is in effect for all three series.

All restarts that happen with 20 laps to go will be single file.

The rule that has been in place calls for double-file restarts up until it was 10 laps to go, with all lapped cars on the inside lane. Drivers were still able to receive the "Lucky Dog" until that time as well.

This season—for Sprint Cup, Nationwide, and Camping World Truck Series—drivers will be eligible to recieve the "Lucky Dog" until there are 10 laps remaining.  However, all restarts from 20 laps will be single file to allow the leaders to race for the win.

“We’ve been talking to the crews, teams, and drivers and we felt like it was a time to make a change,” Pemberton said. “We haven’t taken away the lucky dog and haven’t hurt anybody from getting a lap back.”

Source: Scenedaily.com