Damage to the Allisonville Road overpass at Interstate 465 gives motorists a sign of things to come.

A truck traveling on I-465 March 1 struck a steel beam supporting the Allisonville bridge, which has the least vertical clearance of any bridge spanning the interstate. As a precaution, the Indiana Department of Transportation closed the right north-bound lane of the Allisonville Road bridge.

INDOT already planned to replace the bridge as part of its “465/69 Northeast” rebuilding project, with work on the bridge starting as early as this year. But the traffic-flow part of the plan drew the ire of some Castleton-area retailers last November when INDOT said it was leaning toward the idea of closing the bridge entirely during the replacement.

INDOT said closure would allow it to shorten the replacement time to about seven months versus possibly two years if limited traffic was allowed on one side of the bridge as the other side was being replaced.

The total-closure option would force motorists to seek an alternative crossing of I-465—most likely Keystone Avenue, to the west, or I-69, to the east. Conversely, allowing limited traffic on the Allisonville bridge during construction would cause long traffic backups.

INDOT officials said they’re still weighing which of the two strategies to use during bridge replacement.

The new structure would be higher and designed similar to the I-465 Beech Grove exit on the southeast side, with traffic converging at a single traffic light, atop the bridge. INDOT’s consultants said this configuration results in the best overall traffic flow characteristics down the road.