(Harrisburg) -- PennDot is keeping an eye on increased truck traffic on rural roads in the state where natural gas drilling is growing. Acting Transportation Secretary Barry Schoch says due to the rapid expansion of drilling in the Marcellus Shale formation, the department is building up its enforcement and permitting efforts in those areas. "We've stepped up our resource allocation to that permitting issue and also the monitoring to make sure the Shale companies are making their committments in terms of monitoring and improving the roadway network that they're using," he says. Schoch has told a state House panel PennDot has had to pull some permits, but for the most part, the natural gas industry has done its part by paying for road improvements in the state's northern tier. He says roads and bridges that weren't necessarily designed for vehicles carrying heavy loads will like have to be replaced sooner than planned as a result. Development around drilling sites is also increasing the demand for rail freight service and air travel in the state's northern tier.