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I-85 Managed Lanes are A Success

Baruch Feigenbaum
March 16, 2012, 2:17pm

Despite the initial bumpy ride, the conversion of a stretch of I-85 in Dekalb and Gwinnett counties from a high-occupancy vehicle lane to a managed lane has been a major success. As first reported by my colleague Bob Poole in his Surface Transportation Newsletter, speeds in the I-85 lane have increased compared with speeds before the conversion. The below table compares “before” traffic conditions which includes the months of August and September with “after” traffic conditions which include the months of November, December, and January. Both time periods include seasonal lulls: early August before school starts and late December between Christmas and New Year’s Day. 

Before

After

GP lanes speed (mph)

52.3

54.0

Express lanes speed (mph)

58.5

61.2

GP lanes volume

26,456

26,210

Express lanes volume

3,369

3,024

Total volume

29,825

29,324

Unfortunately a rocky launch, limited information, and continued negative media coverage may be dooming managed lanes projects in other GA locations.

The state had plans to add two new managed lanes in the northwest corridor (I-75 and I-575.) The managed lanes would be open to 3+ person carpools and other drivers who wished to pay a toll. Buses, vanpools, and emergency vehicles would have used the lane for free. The north by northwest project had many of the same benefits as the I-85 project: the choice of a congestion-free ride and reliable transit service. It had the added benefit of new capacity that should dramatically improve travel times. The PPP project was killed for several reasons. One of the main reasons was a media report indicating that two new lanes would increase congestion. This would be the first time in transportation engineering history that adding capacity increased congestion. What did the report really say? 

The proposed project would have added two reversible lanes. In the peak direction, commuters in the regular lanes would have saved between 1-4 minutes on the 18-mile trip the year the project opened. By 2035, with more congestion, the new lanes would save travelers 16 minutes. These commuters would not have had to pay a toll; they could have chosen to ride for free in the general-purpose lanes or they could have chosen to carpool, vanpool or use transit and cut their travel times in half. Congestion in the peak direction would decline substantially saving commuters time in both the general and managed lanes. 

Where would congestion increase? Congestion would increase for drivers traveling against the flow of traffic. At five of the nine locations traffic would theoretically worsen. But traffic would still travel above the 65 mile per hour speed limit. Instead of averaging 75 it would average 67. Only in Atlanta is traffic that is moving faster than the speed limit considered a significant congestion problem. Incidentally, the state considered adding four lanes, two in each direction. However, the costs would force higher toll rates and since I-75 is congested only in one direction at a time, there was not a significant need.

GDOT has other plans for managed lanes. A reversible lane on I-75 south of Atlanta between SR 155 and I-675 is currently in preliminary design. Conceptual studies and conceptual design will finish next month. A managed lane system on Georgia 400 is being presented in several open houses over the next two weeks. Unfortunately, some citizens in Tuesday night’s hearing had several misconceptions. Many were under the misconception that the I-85 managed lane is not working and some were convinced that the state planned to toll existing lanes. Not true. Only new lanes would be tolled. Others were convinced this was some sort of scam to enrich state leaders. Wrong on so many levels. One note on Georgia’s separation of powers: GDOT is overseen by the legislature and SRTA by the Governor. 

To move forward on transportation we need citizens who understand that states have limited financial resources and consider all options instead of hearing the word “tolls” and screaming, “No, No, No.” We need accurate media coverage that reports honestly on how managed lanes have improved congestion instead of enforcing a negative perception of managed lanes. The I-85 project shows managed lanes are a success. But in order to improve traffic congestion on other corridors we need an accurate discussion that highlights the success of the I-85 conversion.


Baruch Feigenbaum is Transportation Policy Analyst


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