HIGHSPIRE, Pa. (AP) -- Speed limits on more than 100 miles of two interstates in Pennsylvania will rise to 70 mph for the first time this summer, with similar increases possible next year on other stretches of roadway around the state, state transportation officials said Wednesday. The Pennsylvania Department of Transportation's announcement comes a day after the Pennsylvania Turnpike Commission raised the speed limit on a 97-mile stretch of I-76 in central and eastern Pennsylvania from 65 mph to 70 mph. About three dozen states already have speed limits of 70 mph or higher. The sections of interstate where speed limits will rise next month include 88 miles on Interstate 80 in northern Pennsylvania's Clearfield and Clinton counties and 21 miles of Interstate 380 in northeastern Pennsylvania's Lackawanna and Monroe counties. The changes are to take effect the week of Aug. 11. The sections of highway were selected because they provide a blend of urban and rural environments that will allow engineers to study the varying effect of the increased speed limits on crash history and work zones, Transportation Secretary Barry Schoch said. Truckers will benefit by moving their products more efficiently, Schoch said. The increased speed limits are unlikely to affect motorists' travel speeds, since they already tend to travel at a speed at which they feel safe, Schoch said. Still, motorists will benefit because the higher speed limit will lower their risk of being ticketed, he said. The most congested sections, such as around Pittsburgh and Philadelphia, will not see speed limits rise, Schoch said. The department, with the help of the Pennsylvania Transportation Institute at Penn State, will study the new 70 mph stretches before deciding whether to create more 70 mph zones, or even keep the zones being created next month, Schoch said. A similar process will happen with the turnpike. Other highways with 65 mph postings include more than 900 miles on interstates 78, 79, 81, 83, 84 and 90, plus Routes 15, 28, 219 and 220, according to PennDOT. Although accident rates are dropping, the biggest contributor to crashes is driving too fast for the conditions, and it is not a problem that the state wants to make worse, Schoch said. Other highways where the speed limit is 65 mph could see increased limits next spring or summer, Schoch said.