a modest proposal (for downtown commuting)

8 02 2010

Recently, we here at The Placemaking Institute have been required to take out our statistical microscopes, which is how we identified this major chokepoint here in Austin:

South Loop 1 at Town Lake

Then Our Most Senior Fellow and Our Most Senior Fellow’s Eminence Grise embarked upon an idealistic idea born from Utopian (if you will) Idealism, the sequence of which is as follows:

1) Average peak hour speed here is about 20 mph; thus this throughput is performing 66% below capacity.

2) TTI’s 1.25 people/auto is probably too high of an average; 1.12 may be more realistic. (It’s interesting to note that, at a recent City Council meeting, Rob Spillar mentioned that Austin has a very high rate of carpoolers even though we don’t provide any support whatsoever for them before adding: “We need to be creative and do things that support them.”)

3) Projected Traffic Volume on South Loop 1 at Town Lake (numbers from CAMPO):

Year

Autos % increase from previous count People/Day(1.12 P/A) People/Day (1.25 P/A)
         
2000 146,000   163,520 182,500
2007 192,000 30 215,040 240,000
2015 221,600 15 248,192 277,000
2025 256,300 15 287,056 320,375

4) Why managed lane(s) are more cost efficient than building/widening existing roadways: Lower costs – Lower environmental impacts – Shorter implementation time frame – Greater flexibility – More active enforcement management – Minimal delays

5 ) What if, instead of a traditional managed lane, it was a dedicated bus lane wherein commuters must pay to use that lane? (Capacity for urban buses is 80-100 passengers [+20% stand] and 600-1,800 passengers/vehicle/day while capacity for articulated buses is 150-200 passengers [+20% stand] and 1,500-2,500 PPVPD.)

6) How many buses and how often should they run to help expedite mobility via a dedicated bus lane? (Assumptions: 30 buses/hour on freeway; there are 15 locations from which the buses pick-up with 30 minute headways, which means that buses are staggered every 2 minutes on the freeway.)

7) Each person dissuaded from driving will save the region @ $812/year in congestion costs (TTI 2007).

3-Lane System Efficiency with Managed Lane    
Purpose: Moving more people with less cars and not just moving more cars more efficiently
Key: A=Autos; B=Buses; H=Hour; L=Lanes; P=Passengers; GP=General Purpose; ML=Managed Lane
               
Scenario 1: 1.12 Passengers/Auto General Purpose Lane, i.e., Existing Condition (3 lanes)
               
Lane Type # A/L/H P/A Total A/L/H P/A/L/H B/H P/B/L/H
               
GP 3 2,000 1.12 6,000 7,526 0 0
      SUBTOTAL 6,000 7,526 TOTAL 7,526
7,526 people = absolute maximum capacity of existing condition  
               
Scenario 2: 2 Passengers/Auto Managed Lane (starting point; supplemented by paid SOVS)
               
Lane Type # A/L/H P/A Total A/L/H P/A/L/H B/H P/B/L/H
               
ML 1 1,500 2 1,500 3,000 30 6,000
GP 2 2,000 1.12 4,000 4,480    
      SUBTOTAL 5,500 7,480 TOTAL 13,480
A net gain of 46 people from Scenario 1, the equivalent of .33 new GP lanes…adding bus lane = 3.33 new GP lanes 
               
Scenario 3: 3 Passengers/Auto Managed Lane (achieved in Houston; national average is +3.0 P/A)
               
Lane Type # A/L/H P/A Total A/L/H P/A/L/H B/H P/B/L/H
               
ML 1 1,500 3 1,500 4,500 30 6,000
GP 2 2,000 1.12 4,000 4,480    
      SUBTOTAL 5,500 8,980 TOTAL 14,980
A net gain of 1,454 people from Scenario 1, the equivalent of .75 new GP lanes…adding bus lane = 3.75 new GP lanes
               
Scenario 4: 4 Passengers/Auto Managed Lane (supplemented by vigorous bus/carpool system)
               
Lane Type # A/L/H P/A Total A/L/H P/A/L/H B/H P/B/L/H
               
ML 1 1,500 4 1,500 4,500 30 6,000
GP 2 2,000 1.12 4,000 4,480    
      SUBTOTAL 5,500 10,480 TOTAL 16,480
A net gain of 2,954 people from Scenario 1, the equivalent of 1.5 new GP lanes…adding bus lane = 4.5 new GP lanes
               
Scenario 5: 5 Passengers/Auto Managed Lane (success breeds success)  
               
Lane Type # A/L/H P/A Total A/L/H P/A/L/H B/H P/B/L/H
               
ML 1 1,500 5 1,500 7,500 30 6,000
GP 2 2,000 1.12 4,000 4,480    
      SUBTOTAL 5,500 11,980 TOTAL 17,480
A net gain of 4,454 people from Scenario 1, the equivalent of 2 new GP lanes…adding bus lane = 5 new GP lanes

1) Each person dissuaded from driving saves the region @ $812/year in congestion costs. Savings without dedicated bus lane for:

Scenario 2 = $37,352; Scenario 3 = $1,180,648; Scenario 4 = $2,298,648; Scenario 5 = $3,616,648

2) Net Passenger Gain after adding a dedicated bus lane (from Scenario 1):

Scenario 2=6,046; Scenario 3=7,454 ; Scenario 4=8,954; Scenario 5=10,454

3) Each person dissuaded from driving saves the region @ $812/year in congestion costs. Savings with dedicated bus lane for:

Scenario 2 = $4,909,352; Scenario 3 = $6,052,648; Scenario 4 = $7,270,648; Scenario 5 = $8,488,648

(sidenote: Also, solely from an O/M point of view, this modest proposal may very well lead to cost efficiencies. TXDOT spends @ $5,000/lane mile/year for maintainence [and can only afford 30% of this] and CapMetro is fiscally constrained from properly maintaining its fleet. Expediting the traffic of people with HOV lanes would increase performance efficiencies for both roadways and buses.)

Machiavelli: “There is nothing more difficult to carry out, nor more doubtful of success, nor more dangerous to handle, than to initiate a new order of things.”

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3 responses

8 02 2010
placemakinginstitute

Anonymous Classically-trained Transportation Engineer: ” In general, the assumptions for scenarios with 4-person carpools, 5-person carpools, and buses assume there is enough demand for these modes to fill up a lane (my interpretation of your scenarios), and experience shows that not to be the case in other areas/projects. Maybe, we might have enough 3+ carpools on Mopac in the peak to justify, but I don’t believe we can get enough demand from higher carpool occupancies to fill a lane with carpools and vanpools. My argument is the same for buses. In my best estimate, I don’t believe there’s enough demand to support full buses with 2-minute headways in the corridor. Nor would the public take kindly to a lane being converted to a bus lane that is empty except a bus every two minutes. The concept of HOT lanes came into being because of the problems associated with underutilized HOV lanes; in many HOV corridors there isn’t enough carpool and bus demand to fully utilize the lanes, leaving them largely empty and underutilized. Pricing allows lower occupancy vehicles in at a price that keeps the speeds from degrading.”

8 02 2010
placemakinginstitute

Thanks so much for taking time the time to critique this. It’s very much appreciated as well as valued. If I were to translate your engineer-speak into one sentence, would this suffice?: “Austin isn’t anywhere near close to being ready for such an idea.”

8 02 2010
placemakinginstitute

Anonymous Classically-trained Transportation Engineer: “Who knows, Austin is a progressive community. But I haven’t seen anything that demonstrates Austinites to be different than other drivers in terms of their behavior. Keep the ideas coming. We desperately need fresh ideas.”

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