Road Zipper Newsletter: Let’s define one of the terms that we’ll be using in this interview. What does the phrase “future flexibility” mean to you?
Chris Sanders: I don’t think that traffic engineers can be expected to accurately forecast highway capacity requirements when we look forward 20 to 40 years into the future. We don’t know exactly how many vehicles will be on the road, or if cars and transport vehicles will have a similar design to what we see today, or even whether or not those vehicles will have human drivers. This makes it very difficult to design for specific future road capacity requirements. What we do know is that if long-term patterns hold, there will be more people, more drivers, and more demand, so the best practices now include designing future flexibility into our urban highway planning. This is particularly important for tunnels and bridges. The cost of adding an additional 18” in the initial construction phase to allow space for a moveable barrier is really insignificant compared to the cost of trying to add additional space in the future when you want to manage lanes and mitigate congestion. I know a DOT engineer who always says, “Never build a fixed median in a city.” I think that is the real spirit of future flexibility.
RZN: What would you say are the real benefits of planning with future flexibility for DOTs and road agencies?
CS: When agencies plan ahead and consider future flexibility in the initial stages, making the transition to managed lanes can be done either immediately or in a short amount of time. If there was no future consideration in the original design, you may wind up with a situation where it’s difficult to build crossovers or the system elements don’t fit on the roadway, and that leads to significant additional time and money to create functional managed lanes. It’s the difference between having “on-demand” scalability compared to starting over with an entirely new concept.
RZN: How do road users benefit from this kind of road planning and execution?
CS: All road users benefit from an intelligent, thoughtful approach to congestion mitigation. When roadways that were designed for future flexibility become impacted with rising ADT counts, the issues can be addressed immediately and with fewer delays. We can minimize user delay, wasted fuel and rising freight costs by being prepared for a problem that we know is coming, rather than waiting until it is too late to act responsibly. On the I-15 in San Diego, they built four lanes in between the general purpose lanes and put a moveable barrier down the middle for future congestion management. They didn’t need to move it for several years, and now they move it every day during the week. They were ready when the need arose, and that’s what future flex planning is all about. I’m happy to see more and more agencies thinking along these lines, but we also need to make sure that the public understands why we’re spending transportation dollars on a system that may not be immediately necessary.
RZN: Do you think that tolling will be an inherent part of flexible design in the future?
CS: Well, tolling is here to stay. It’s not going to go away, and it can be beneficial to the managed lanes facility. When there is additional capacity in an HOV system, it makes sense to convert to HOT lanes and let ineligible vehicles use the lanes for a fee because tolling will almost always pay for the facility’s operating costs. You may not recover all of the capital costs, but operational cost is always a concern for DOTs, and tolling alleviates that concern. I think it’s a good idea, especially if it helps swing opinion to design with flexibility.
RZN: Do some projects benefit more than others from future flex design? Where do you see the most benefit?
CS: There are sections of the National Highway System, particularly those highways that link between urban areas, that can easily be widened. A 2/2 roadway is difficult to reimagine as a managed lanes facility, and there would probably be more benefits widening the road to a 3/3. In urban areas, right-of-way is much more expensive and construction is more difficult and time consuming, so this is where future flex design offers the most options and cost savings. In my opinion, tunnels and bridges top the list, but we shouldn’t forget contraflows on highways or separated structures. It turns out that the most efficient modes of transportation are bicycling and walking, with single passenger vehicles being one of the most inefficient. We need to design roads that promote and facilitate efficient transportation whenever possible. Bus Only Lanes and Rapid Transit programs can create major efficiencies for both arterials and freeways. The Katy Freeway in Houston is a great example of, “If you build it, they will come.” I think that freeway is 26 lanes wide at the widest, and there is a famous picture that shows all the lanes gridlocked in one direction while the reverse commute has extra capacity that could be better utilized. We need to do a better job of building flexibility into our roadways and moveable barrier has been used with great success to help public transit operate more reliably which increases ridership.
RZN: There are plenty of people who feel that “cattle chutes” fall under the heading of future flexibility. Although they are created with permanent concrete barriers, cattle chutes are reversible lanes that offer more capacity to the peak traffic direction. Do you agree with this definition, and how do the benefits of a cattle chute compare to a moveable barrier installation?
CS: I think it’s fair to categorize them similarly, but cattle chutes and moveable barrier installations have some different pros and cons. Cattle chutes may allow for some savings in both capital and operational expense, but their flexibility is limited to the initial design. I usually see cattle chutes with two reversible lanes and two shoulders, because they are typically built where there is some extra room. The process of reversing a cattle chute is difficult because you have to guarantee that the last car is out of the chute before you can reverse the lanes, and there is liability there for the agency. Many moveable barrier systems can create immediate flexibility, and you can start to close the lane to give it back to the general public just after the last vehicle passes through. Cattle chutes also tend to take up a larger footprint than a moveable barrier facility that manages the same number of lanes. When you have the room to build it, a cattle chute can make good sense, but this is a questionable practice in urban areas where space is at a premium. A moveable barrier facility can be restructured in almost unlimited ways based on longer term traffic patterns, and you can even remove the system and reinstall it at a different location with greater need, so I don’t think that a cattle chute will typically be the most efficient way to move more traffic in urban areas.