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As Managed Lanes Increase, Growing Pains Arise

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According to an article by Susan Buse in the annual Tolling Review produced by Thinking Highways, as of the end of 2014 there were 28 tolled managed lane projects in operation in 10 states plus Puerto Rico, with another 18 either under construction or nearing construction. The projects already in operation include 350 miles, with another 500 miles of express lanes in the pipeline. So rather than trying to provide an overview, my focus this time is on emerging growing pains.

One problem is that most elected officials—and even many transportation professionals—don’t yet understand that an express lane priced to maintain uncongested traffic flow at LOS C is the virtual equivalent of an exclusive bus lane. That lack of understanding is evident right now in the Washington, DC metro area, where both the Maryland and Virginia DOTs are considering adding managed lanes to congested urban Interstates. In Maryland the debate is over whether to add bus-only lanes or express toll lanes to I-270. And in Virginia, VDOT’s plan for adding express toll lanes to 25 miles of I-66 outside the Beltway also calls for expanded express bus service in the median! This is a waste of pavement. Repeat after me: a priced managed lane is a virtual exclusive busway. It’s not either/or; it’s both/and.

Another problem is shared between federal and state/local officials: reluctance to increase the occupancy requirement for free HOV passage from two to three. In Los Angeles, the converted HOT lanes on the Harbor Freeway (I-110) are so successful that first-year toll revenue was nearly double the projection—but because two-thirds of the vehicles during peak periods are two-person freebies, even with tolls at the maximum rate allowed, the lanes are getting congested during peak-of-the-peak times. So LA Metro’s remedy is to close the lanes to paying customers, to preserve mobility for the HOV-2s and the (very successful) new express buses.

HOV lanes all over the Los Angeles and San Francisco Bay Area are in blatant violation of the federal standard of 45 mph or better 90% of the time—but there is no federal requirement that in those cases occupancy be increased from two to three. If Congress made that mandatory, local officials would escape blame, and the revenue potential of converted HOV lanes would soar, generating funds needed to expand the system into the express lanes networks that both metro areas claim they will build. That will remain a pipe-dream as long as they are giving away most of their capacity to two-person carpools (a great many of which are fam-pools).

Florida DOT bit the bullet on going from two to three-person occupancy when it did the award-winning conversion of the failing HOV lanes on I-95 in Miami into the wildly successful I-95 Express Lanes. So did Georgia DOT on its I-85 managed lanes project. Washington State DOT is seriously considering doing likewise before it opens 17 miles of new and converted HOV lanes on I-405 between Bellevue and Lynwood this fall. I hope they persevere and do it.

Another problem is deciding what kind of access to provide between general purpose traffic lanes and managed lanes. Many HOV lanes around the country are continuous access—cars can enter and exit wherever they wish, and the separation between GP and MLs is simply a painted line or lines. Most managed lanes, by contrast, have only limited access, with entry and exit points miles apart (which led FDOT to refer to express lanes and “local lanes” to emphasize the difference). In California, HOV lanes in the Bay Area were developed with continuous access, while those in southern California have always had designated entry and exit points, designated by signs and openings in the pavement striping.

With both regions planning managed lane networks, it looks as if politics is leading the Bay Area to plan its network not only with continued HOV-2s-go-free but also with continuous access. If they do that, my prediction is failure, for two reasons. First, the performance of the tolled lanes will be degraded by the “friction” effect, well-documented by researchers at UC Berkeley and UC Riverside. When the GP lanes slow to a crawl, traffic in the adjacent HOV lane does the same thing. Why? Because drivers in the HOV lane anticipate that any time the HOV lane goes slightly faster, frustrated drivers from the GP lanes will dart in front of them. This phenomenon does not happen on HOV lanes in southern California. You can’t sell people faster, reliable trips on lanes that often go as slowly as the free lanes. Moreover, the Bay Area network cannot be created simply by converting all existing HOV lanes to priced lanes, because there would be numerous missing links on freeway segments that have no HOV lanes. So the revenue needed to build all that new capacity cannot be generated if the converted HOV lanes give away most of their capacity to two-person carpools.

One more problem that’s starting to appear is congestion at the point where a managed lane ends and traffic on it has to merge into the GP lanes. The new I-95 Express lanes in northern Virginia are experiencing this at their southern terminus on Friday afternoons and at some times on weekends, where five lanes of traffic must merge into three, and there is a similar problem at the northern end of the Beltway (I-495) Express lanes. The best remedy is clearly to add capacity by extending the managed lanes through the bottleneck to the point where traffic demand is significantly lower. That’s what FDOT is doing with the 14-mile extension of the Miami I-95 Express lanes to Ft. Lauderdale, with further northward extensions planned thereafter.

These problems are partly growing pains, partly misunderstandings of how managed lanes work, and partly conflicts of ideas (e.g., that more lane capacity is bad, unless it is used only for buses). My hope is that the example set by managed lane projects that are allowed to run like businesses—offering faster and more reliable trips for a market price—will demonstrate the better way forward.

(This first ran in Surface Transportation Innovations April 2015)
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