"The old bridge . . . wasn't physically capable of handling [the weight of] commercial trucks," said John O'Hern, the authority's deputy executive director.
Also to be considered is the effect of commercial trucks on the pavement and bridges and whether the overpasses are high enough, said Veronique Hakin, executive director.
Generally, older parkways, such as those in New York, were designed specifically for cars and have bridges with clearances that won't accommodate a commercial truck or tractor-trailer. That is the case with some of the original Garden State Parkway stone overpasses with arches in Middlesex and Union Counties.
"There are a whole bunch of issues we have to get to," Simpson said. "The first is: If you wanted to, could you? If you could, would you want to? We haven't gotten to could you."
If the infrastructure allows it, one factor in favor of commercial truck traffic on the parkway is that it is a money maker, said Neil Gray, director of governmental affairs for the International Bridge, Tunnel, and Turnpike Association.
"It pays proportionally more than cars do because of the weights," Gray said.
The driver of a car traveling the 113-mile length of the New Jersey Turnpike would pay a $9.05 cash toll, compared with $37.15 for a six-axle truck.
Another consideration is using the parkway to take traffic off other highways.
"I'd suspect people are looking at traffic flows and saying we have a logical link" by using the parkway, Gray said. "A big part has to be looking at regional traffic flows and how to move that traffic."
Trucks crossing the Raritan River now must use Route 35, Route 9, or the turnpike.
"We're trying to get all the capacity we can out of the system," Simpson said. "I asked about that a while ago as a reliever to other roadways."