A new interchange on Interstate 78 might be the ultimate solution to reduce future traffic congestion in western Lehigh County.

That interchange could be built where Adams Road now passes over I-78, about two miles west of the Route 100 interchange.

Its primary purpose would reduce heavy tractor-trailer traffic at the busy Route 100/I-78 interchange. But it also should reduce traffic congestion on Hamilton Boulevard and the Route 222 bypass.

Traffic around the I-78/ Route 100 interchange “is a nightmare and it’s only getting worse, because more and more development is occurring,” predicted William Erdman, project manager at Keystone Consulting Engineers.

“There’s only one solution out here in this area and that’s a new interchange.”

Erdman said construction of a new interchange may be 10 or 20 years away but indicated it’s time to take steps to anticipate future traffic needs.

A joint effort is being initiated by Upper and Lower Macungie townships to improve traffic flow, explained Erdman, who is the engineer for both townships.

As a first step, Upper Macungie has nearly completed a traffic enhancement study to determine what improvements, if any, can be made on six-lane-wide Route 100 at I-78.

On Thursday night, Lower Macungie commissioners will vote on doing a similar $10,000 study at the Hamilton Boulevard/I-78 interchange, which is more than six miles away from the Route 100 interchange.

Because all the interchanges involve state roads, Erdman said the studies done in the two townships will be combined into one report that will be presented to the Pennsylvania Department of Transportation.

The intent of both studies is to determine if any traffic flow improvements can be done around both I-78 interchanges.

By looking at every possible alternative, said Erdman, the report that results from those studies will set the stage for a future interchange west of Route 100 “as the only real solution in this area.”

He said a new interchange may be needed even if improvements are made around both existing interchanges, if traffic congestion continues to build.

But Erdman stressed the studies are not being done for the sole purpose of going to PennDOT and saying “put in an interchange,” which would cost millions of dollars.

Tractor trailer traffic is a major contributor to the increasing congestion. They service huge warehouse/distribution facilities concentrated around the I-78/Route 100 interchange, as well as other “big boxes” farther south off Route 100 in Lower Macungie. More of those facilities will be built in the future.

If that Route 100/I-78 interchange becomes too congested, trucks leaving both townships may start looking for other ways to reach I-78. That could mean they will go east on Route 222 or Hamilton Boulevard to get on the interstate.

Erdman said trucks coming north from Lower Macungie to a new interchange would turn off Routes 100/222 and take Grim Road and Nestle Way, both four-lane roads, to Adams Road. He said most tractor-trailers head east on I-78, toward New York or New Jersey.

Erdman said I-78, Hamilton Boulevard and the Route 222 bypass are the three major east-west traffic corridors through western Lehigh County.

He explained traffic in each township affects the other township and “problems on one corridor will impact the other corridors.” For example, if I-78 is closed because of an accident, traffic increases on Route 222 and Hamilton Boulevard.

Erdman maintained adding that interchange in Upper Macungie will reduce traffic pressure on the Route 222 bypass and Hamilton Boulevard, which will benefit Lower Macungie. He called it “a ripple effect.”

“It’s truck traffic we’re most concerned about,” said Erdman. “We want to keep it on I-78 as much as possible. That will help the rest of the townships.”

But he added all vehicles, not just big trucks, are going to take “the path of least resistance.”

The planned Hamilton Crossings shopping center -- with a Costco, Target and other stores -- will put more car traffic on Hamilton Boulevard and Route 222 when it opens by 2015 between those roads in Lower Macungie.

Cost of a new interchange

Erdman said the idea of a new I-78 interchange first showed up “quite a few years ago” in a traffic study done for Upper Macungie Township. He said PennDOT officials also once talked about putting a rest stop in that area, and the possibility of combining both projects was discussed. “For some reason it never went anywhere.”