Sustainable Freeways – Overview

Freeways, New and Improved!

Full Article (18 pages)
By Michael Brown, PE, AICP
President, Urban Innovators

Finally freeways CAN run well again…

  • without being widened again!
  • without inducing more demand!
  • and with a good shot at political viability!

Executive Overview
(3-page summary)

What would a “Successful, Sustainable Freeway” look like? It would be uncongested even in peak hours, but the reliable high speeds would not induce more demand nor contribute to more sprawl. It would do this without needing to ever be widened, and hence would have only maintenance costs rather than “Big Dig” expansion costs.

Sounds too good to be true? It’s becoming more possible all the time. A concept called Managed Motorways will be coming first to Denver then shortly after to Salt Lake, and we at Urban Innovators are imagining enhancements to that system that could finally help freeways stop working against sustainability. The key aspect of Managed Motorways is enhanced ramp metering, with algorithms to adjust on-ramp wait times to prevent mainline stop-n-go. But like widening, this new way to get speed/capacity gains will induce demand, so it shouldn’t be long before talk of Big Digs returns.

Distance-based congestion pricing can manage demand to available supply, but so far it’s been politically infeasible. We have devised a “Congestion Credits” strategy that merges Managed Motorways with Congestion Pricing through a mechanism where many and perhaps most 5-pm drivers could still travel a fully-priced, “all lanes must pay” freeway without having to pay a dime. Majority for free would make congestion pricing much more politically possible, and would also give more reasons to ride transit, travel in off-peaks, etc. for those who would end up paying.

If you have time to read the full article, hopefully you can see what we’re seeing. If you have less time, below are some of the key facts about freeways, Managed Motorways, and how our Congestion Credits system could work. 1-8 describe why freeways fail, and how Managed Motorways can prevent that, at least temporarily. 9-12 highlight our Congestion Credits strategy, which can help a Managed Motorway operate for decades without widening and with much less, if any induced demand. 13-18 discuss potential benefits of the joint MM+CC system.

Key Concepts

  1. Freeway Capacity vs Throughput: Capacity is about 2,200 vehicles per hour per lane – a red-line that freeways cannot go above. If more than this attempt to enter, the freeway will collapse into stop-n-go, and will instead see actual throughput drop to 1,500 vphpl or less – just 70% or less of maximum capacity. This 70% or less is “every day, USA.”

  2. Existing ramp meters are not smart enough to prevent more than 2,200 from entering. They organize flow and delay collapse, but there are no mainline sensors telling ramp meters when they’re letting on too much traffic. Just like a 20-amp circuit will “break” with an attempt to draw 22-amps, a freeway also “breaks” above 2,200 vphpl.

  3. Solution: Stop letting too many vehicles in! Managed Motorways (MM) includes mainline sensors and interconnected ramps so that computer algorithms can sense pending breakdown and adjust ramp delays in order to “hover” at about 95% efficiency – close to, but not above the red line.

  4. Like rice through a funnel: So far, the easiest way for the public to comprehend the problem and get on-board with longer ramp meters has been to see a “rice through a funnel” experiment, where dumping it all in at once proves slower than metering it.

  5. Widen on-ramps? MM causes ramp delays to increase, but mainline delays decrease by much more. However, since ramps increase, there may be a need to widen on-ramps for more storage.

  6. Current Examples: Managed Motorways has been implemented by VicRoads in Australia, with 25% more vehicle throughput during peak periods, a 50% reduction in overall travel delays and 20-50% crash-reductions along some segments. It will soon be implemented in Colorado, and shortly after that in Utah.

  7. Replacement for HOT lanes? There may be no more need for HOT lanes since Managed Motorways are proving politically possible, and can ensure that ALL lanes will run at near-maximum performance. HOT lanes provide option to “buy your way out of congestion” or to “pay the price” with your time rather than money. MM allows the same options, but does so at on-ramps without expensive mainline construction to separate fast lanes from failed lanes.

  8. Managed Motorways will cause induced demand: Since it’s smooth sailing once you’re on, MM tends to favor long trips. Over time, this encourages longer commutes (induced demand) and accelerates sprawl, just like widening a freeway always does.

  9. Distance-based Congestion Pricing dampens induced demand, but is politically toxic: Congestion Pricing (CP) can dampen sprawl and would be sustainable for longer than MM with no distance-pricing option. But so far pricing is politically infeasible, as it requires 100% to pay a hated “double-tax” to drive at five.

    Sometimes on-ramps need to be widened so that Managed Motorway systems have a place to store vehicles. Otherwise they get “stored” in a long parking lot formerly known as “the freeway.”
  10. Can “Congestion Credits” increase political feasibility? We propose adding a “Congestion Credits” approach to help make Pricing politically possible. For instance, provide a choice at on-ramps to pay $2.00, or to wait 6- minutes and collect a $2.00 credit on your transponder. Then you can travel 15 to 20 miles with your $2.00 credit. This makes 5 pm travel free for all but the longest trips. Though still perceived as a double-tax on long trips, it can be revenue neutral or even an overall tax cut, even for long trips, since there’s less need to build “Big Digs.” Can this create enough political viability to finally test pricing somewhere?

  11. Use proceeds to make transit free: Many will argue that paying any extra will hurt low-income drivers. Use revenue from those who pay to bypass ramp queues, and from long trips, to make express buses or parallel trains “Free at Five.”

  12. Make Ramp Bypass Lanes Transponder Only: Allowing high-occupancy vehicles to use bypass lanes for free is fine, but don’t run it with an honor system. Create a program for free or reduced rate transponders, and let local politics determine who gets them: Express buses, registered car/van pools, low income, low-emission vehicles, etc.

  13. Return on Investment: A 95% efficient MM or Pricing/Credits system offers huge societal benefits over today’s 70% or less systems. Urban Innovators tested such a system using Salt Lake’s travel model and the TREDIS economic analysis package, and found $50-Billion in benefits over 25-years – a Benefit/Cost of 50 to 1 if they spent $1-Billion. Actual cost may be much less.

  14. Tune-ups are always cheaper than overhauls: As an analogy, if your V-8 engine was sputtering on only 5-cylinders (70%), would you think it cheaper to get a “tune up” and stop the sputtering so it will always fire on all 8? Or would you rather “widen the engine” and install 12-cylinders so that when it sputters to 70% efficiency, you’ll at least still have a V-8’s worth of power? In both cases you get back to 8 cylinders worth of horsepower! On top of a 50:1 Return on Investment, the higher throughput and steady reliability of any 95% system means that many expensive capacity projects (effectively 12-cylinder upgrades) can be downsized or eliminated, potentially reducing overall net taxes.

  15. Discouraging some from using the freeway will only make alternative routes… Better! Counterintuitively, MM or Pricing models could make alternative routes less congested. Yes, some drivers will divert to alternates, but higher throughput on freeways might mean that for every driver who avoids the freeway, there could be two already on alternative routes who will now come back.

  16. Double-tax optimization is cheaper than status quo single-tax inefficiency: Claims of double-taxation had some merit with traditional congestion pricing, since 100% had to pay with money. Pricing w/Credits reduces the strength of that claim, and when factoring in less need for freeway expansion, a fuel tax + peak hour system optimization fee, which can be paid by many in time, will still prove to be less money even to those who pay the fee than a single fuel tax. That’s because collapse to stop-n-go means taxes will increase substantially to pay for “V-12” freeway expansion, when all we really needed was to pay a little, with money or time credits, for an efficiency tune-up.

  17. Optimization should rank high in select-by-performance frameworks: Performance-based planning can aid decision-makers who may otherwise be nervous about how to craft educational sound bites for a potentially angry public. “Don’t blame me! This had the highest ROI for achieving our goals.”

  18. Ideas Worth Trillions: These concepts are potentially worth trillions if applied nation-wide. In our estimation, this is truly a “New and Improved” formula for operating freeways in a way that will make them both operably and environmentally more sustainable.

Note: Comments below come from both those who read just the overview as well as those who read the full article.

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