Work to build Jefferson County’s first Diverging Diamond Interchange, or DDI, is reaching a significant milestone.
Next week, ALDOT will install girders for the new eastbound bridge over I-59/20 at McAshan Dive in McCalla, weather permitting.
To set the girders on the southbound side, crews will use rolling roadblocks on I-59/20 between I-459 and Exit 104. Setting the northbound girders will require similar roadblocks between Exit 100 and Exit 104 on the interstate.
The 15-minute rolling roadblock intervals will take place on the nights of Wednesday, February 25 and Thursday, February 26, from 11:00 pm until 5:00 am.
The inside lane will remain closed each night for crane operations starting at 7:00 pm.
Navigating a Diverging Diamond Interchange
As drivers approach one side of the bridge, the design will allow traffic to gently transition from the right side to the left and then back again at the other end of the bridge.
Since traffic travels on the left side, all left turns are made without having to cross opposing traffic.
Federal Highway Administration research shows DDI’s are more cost effective, efficient and safe.
- Lower construction costs up to 75 percent
- Decrease conflict points by nearly half
- Increase traffic efficiency up to 30 percent
Work on an additional DDI at I-65 at Lakeshore Parkway starts next week in Homewood, with plans to utilize the design at Hoover’s future Exit 9 on I-459.
The McAshan Drive DDI should be open to traffic this fall.
