The proposed Roswell Road at I-285 bridge widening project seeks to improve safety and reduce congestion at the interchange by creating additional dedicated left turn lanes from Roswell Road in both directions.
The existing Roswell Road Bridge over I-285 consists of five 10 foot wide lanes. Four of these lanes (two in either direction) are through lanes across the bridge. The middle lane (fifth lane) is split and serves as a left turn lane to access the east and westbound I-285 corridor. The alternating use of this one lane for both directions effectively reduces the turn lane storage to only 150 feet. This storage is not adequate to satisfy turning queues which results in turning vehicles spilling out into through lanes and blocking one through lane in each direction. This congestion also blocks one of the two left turning movements from each of the interstate off ramps.
An additional existing problem is a lack of ramp storage in the eastbound and westbound direction at the current ramp meters. This lack of storage allows the ramp traffic to spill back to the signalized intersection and further congest Roswell Road.
The proposed project intends to widen the existing 64 foot wide bridge to create six 11-foot wide lanes. The project would maintain the four through lanes (two in either direction) but would create two center lanes dedicated to one left turn lane for the I-285 eastbound direction and one left turn lane for the I-285 westbound direction. The widened bridge would be 80-feet wide and would require the widening of the three piers that currently support the existing bridge.
The project also proposes to widen the ramps onto I-285 in both directions from one on- ramp lane to two on-ramp lanes. This widening would double the queue length of the ramp meters.
A 4.5 to 14 raised concrete median would be constructed along Roswell Road on the approached to the bridge. In the southbound direction on Roswell Road, the median would be approximately 280-feet in length. In the northbound direction on Roswell Road, the median would be approximately 390-feet in length. These medians serve to control access to the turn lanes and prevent dysfunctional turning movements. Allen Road, which intersects Roswell Road just north of the interchange, would be reconstructed to a right-in/right-out only as a result of the median. This would change access to some businesses along Roswell Road.
This project is proposed to be constructed entirely within existing 32 to 75-foot wide right of way with no needed easements.
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