The Chattanooga Zoo’s new entrance plaza along Holtzclaw Avenue — with its plaza, gift shop and office buildings — is busy this summer.

Revenues are up as visitors on “staycations” check out new features. But there’s one thing the new, $4.5 million gateway is missing.

There’s no direct way to get there. Access to the zoo, as it has for years, continues to be through the Third Street entrance.

Plans were submitted to the Tennessee Department of Transportation last fall and were approved, according to zoo director Dardenelle Long. But the Tennessee Valley Railroad leases the rail track that runs along Holtzclaw from Norfolk Southern and uses it for sightseeing excursions. For that reason, Norfolk told the zoo it had to put in signal lights, which would cost nearly $70,000.

“So we decided we’d have to wait on that,” Ms. Long said.

The Friends of the Zoo has set aside $25,000 for completion of the Holtzclaw Avenue entrance, Ms. Long said. Now, Chattanooga Parks and Recreation administrator Larry Zehnder is trying to find the additional $45,000 needed for the signals.

“The entrance road is important, and one that we want to see completed,” Mr. Zehnder said. “And it’s the dollars and cents that are the only thing in question now that the railroad has approved the crossing.”

To get approval for the zoo’s railroad crossing, Chattanooga has agreed to close two other crossings —one in East Chattanooga and one in Alton Park, according to Tim Andrews, TVRM president.

“If you want to open a crossing someplace, you have to find another one to close,” said Bill Schafer, director of strategic planning for Norfolk Southern. “But for the cooperation of the city of Chattanooga, we would not have approved a new crossing at the zoo.”

Mr. Zehnder said he’s looking at his capital budget to see if there’s any money that may not be needed right way.

“It’s in the process now, but nothing’s been determined,” he said. “If we can identify the dollars, we should get moving and have it done by the fall.”

During the high season from April through November, TVRM makes three round trips a day, Mr. Andrews said.

There were two accidents, neither with injuries, in Chattanooga last year involving passenger trains and cars, one at a Bragg Street crossing and the other at Main Street and Holtzclaw Avenue, he said. The trains travel at top speeds of 20 miles an hour, he said.