They're hoping the increase in speed alone will entice truckers back onto the toll road. Highways 20, 2, even 322 is getting beaten up pretty bad because of the truck traffic. They're hoping to get trucks off those roads and back onto the big road, and they'll try anything short of reduced tolls, like increased speed, to do it. Next they'll be decreasing speeds along sections of hwy 20. Right now it's only half an hour, maybe 45 minutes longer to take the secondary roads, depending on where you're going, but if they can turn that into an hour and a half or more, people will go back to the toll roads. (Or, truckers in droves will use hwy 20 to clog things up even more until they raise the speed limit back again).