I15 Express Lanes Dynamic Pricing Project

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I-15 Express Lanes Dynamic Pricing Project

• by Cameron Kergaye

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Executive Summary

• I-15 through SLC carries unique challenges
  regarding Express Lanes.
• Distinctive Advantages/Disadvantages to each type
  of tolling strategy.
• Several different bases for assessing the toll.
• HNTBs preliminary recommendation of a Zone
  Tolling approach based on current options.
• I-15 Express Lanes Dynamic Pricing Algorithm.

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Purpose

• To discuss issues related to the dynamic pricing
  algorithm for the I-15 Express Lanes in Salt Lake
  City.
• Show options for dynamic pricing.
• Evaluates the advantages and disadvantages of
  each option.
• Recommends of a preliminary dynamic pricing toll
  strategy and algorithm.
• Outlines the overall operation of a dynamic
  pricing algorithm.

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Corridor Description

• Express Lanes HOT or Managed Lanes.
• The Corridor is composed of two segments
• Southern segment
• Exit 278 (American Fork) to Exit 313 (N. Salt
  Lake).
• 35 miles in length.
• Northern segment
• Exit 322 (Farmington) to Exit 328 (South Layton).
  
• 6 miles in length.

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Corridor Description
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The Existing Express Lanes 

• I-15 has one Express lane in each direction.
• Exit 269 in Orem to Exit 309 in Salt Lake City.
• Open 24 hours a day to
• vehicles with 2 or more occupants
• motorcycles, emergency vehicles, buses,
  clean-fuel vehicles
• vehicles displaying an Express Lanes decal on the
  windshield.
• Existing Express Lanes separation
• Painted double-white striped line. Ingress and
  egress points
• access points - designated by a transition to a
  dashed line.

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Access Point on NB I-15
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UNIQUE CHALLENGES

• Length - longest HOT/Managed Lanes corridor in
  the US.
• Complexity About 30 access points each
  direction.
• San Diego (20 miles, 10 access points each
  direction)
• Minnesota (10 miles, fewer than 5 access points)
• Seattle (9 miles, fewer than 5 access points)
• Density - in SLC, the Corridor runs through an
  urban center.
• Most HOT Lanes/Managed Lanes run from lower
  density to high-density.
• In Salt Lake City, During the morning peak,
  congestion builds as one approaches the urban
  center, and then declines as one travels away
  from the urban center.

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TOLLING STRATEGY OPTIONS

• Option 1 Fixed or flat fee tolling.
• (Charge all customers a flat fee to enter
  Express Lanes.)
• ADVANTAGES Simplicity, Capacity.
• DISADVANTAGES Equity, Management.
• Option 2 Per-mile tolling.
• (Charge customers per mile, rate variable.)
• ADVANTAGES Equity, Predictability.
• DISADVANTAGES Rate calculation, Equipment,
  Operations.

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TOLLING STRATEGY OPTIONS

• Option 3 Barrier tolling.
• (Dynamic tolls would be charged at each
  tolling barrier)
• ADVANTAGES Minimization of tolling equipment.
• DISADVANTAGES Equity, Toll complexity,
  Operations.
• Option 4 Zone tolling.
• (Customers would be charged a toll to enter
  each zone
• ADVANTAGES Equity, Operations, Algorithm
  Complexity.
• DISADVANTAGES Toll Complexity.

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BASIS OF PRICING ISSUES

• Fundamental Basis for Assessing the Toll?
• Travel time savings.
• Level of service.
• Volume.
• Translating travel time savings
• The Corridor is very long
• There are numerous access points
• The densest area is in the middle of the Corridor
• The percentage of long-distance thru trips is
  probably minimal.

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BASIS OF PRICING ISSUES

• Other policy-related questions
• Is the dynamic toll the same at all points of
  entry?
• Is the toll consistent once a customer enters the
  Express Lanes?
• Should the tolling policy include a minimum and
  maximum toll rate?

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RECOMMENDED APPROACH

• Recommendation
• Zone Tolling approach
• Why?
• considerable advantages
• limited shortcomings
• See Table 1 (Next Slide)

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RECOMMENDED APPROACH
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Fundamental Concepts of Zone Tolling

• All zones typically about 5-10 miles in length.
• Multiple access points into the Express Lanes.

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Fundamental Concepts of Zone Tolling

• Shorter zones in urban areas, Longer zones in
  suburban areas.
• Major interchanges were used as zone boundaries,
  when possible.

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Fundamental Concepts of Zone Tolling

• The flowchart illustrates how the algorithm would
  function for each zone.

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Fundamental Concepts of Zone Tolling

• Flowchart (Continued)

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Dynamic Pricing Algorithm Step 1/6

• 1. Is it midnight? Yes, go to block 2. Otherwise,
  it proceeds to block 3.
• 2. The time and interval are reset to zero toll
  is set to minimum and Z value (relative value
  of maintaining free-flow conditions on EL) is set
  to base value.
• 3. n n 1. If the time is not midnight, then
  the interval increments by one.
• 4. Record data for 1 time interval system
  records speed and volume data in EL, and speed
  data in GP (for each segment).

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Dynamic Pricing Algorithm Step 2/6

• 5. Calculate key traffic parameters for each
  direction of travel
• a. S(GP) for each segment within a zone.
• b. S(EL) for each segment within a zone.
• c. V(EL) for each segment within a zone.
• 6. Identify critical parameters
• a. Vcrit Max flow rate for all EL segments, in
  vph.
• b. S(GP)crit Lowest avg speed for all segments
  per zone.
• c. S(EL)crit Lowest avg speed for all segments
  per zone.
• 7. Calculate remaining capacity in critical EL
  segment. V-rem is the functional capacity of EL
  minus the critical volume (Vcrit).

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Dynamic Pricing Algorithm Step 3/6

• 8. Is V-rem0? This checks if the critical EL
  segment is operating over-capacity. If yes,
  proceed to block 9 otherwise block 13.
• 9. Is S(EL)crit,n S(EL)min? This checks if the
  speed in the critical EL segment is above the
  minimum desired speed. If yes, proceed to block
  10 otherwise block 13.
• 10. Display zone toll (1). The critical segment
  of the Express Lanes is operating over-capacity,
  but the lanes are maintaining an acceptable
  speed. The zone toll (tolln-1) should be
  incremented upward (by tollinc) and posted at
  zone entry points. Proceeds to block 22.

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Dynamic Pricing Algorithm Step 4/6

• 11. Is S(EL)crit,n S(EL)min? (2) This checks if
  the speed in the critical EL segment is below the
  minimum desired speed. If yes, proceed to block
  12, otherwise block 15.
• 12. Is D(EL)crit,n gt D(EL)max? If flow is below
  capacity but speed is also below min acceptable
  speed (i.e. during overnight hours or during
  incidences) then proceed to block 13, otherwise
  block 15.
• 13. Display CLOSED TO SOVs. This represents two
  conditions
• a. Condition 1 The critical EL segment is
  operating above capacity with unacceptable
  speeds.
• b. Condition 2 Flow in the critical EL segment
  is below capacity with excessive density.

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Dynamic Pricing Algorithm Step 5/6

• 14. Maintain zone value. When EL are closed to
  SOVs the value of Z should be maintained at
  current level. Proceed to block 24.
• 15. Calculate preliminary toll (where critical EL
  segment is not operating at capacity)
• a. V-remn Cap Vcrit 1675 1400 275 vph.
• b. p-tolln Zn-1 / V-remn 250 per hour / 275
  vph about 90.
• 16. Is p-tolln tollmin? If yes then proceeds to
  block 17, otherwise block 18.
• 17. Display zone toll (2) then proceed to block
  21.
• 18. Is p-tolln gt tollmax? If yes then proceed to
  block 19, otherwise block 20.

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Dynamic Pricing Algorithm Step 6/6

• 19. Display zone toll (3) then proceed to block
  21.
• 20.Display zone toll (4) where the actual toll is
  set to the preliminary toll (from block 15).
• 21. Is S(GP)crit,n S(GP)min? If yes proceed to
  block 22, otherwise block 23.
• 22. Increment zone value by Zinc. As conditions
  deteriorate in GP, relative value of free-flowing
  trips in EL increases. Proceeds to block 24.
• 23. Decrement zone value by Zinc. The Z value can
  only be reduced down to Zbase. Proceed to block
  24.
• 24. t t3 minutes. This process is repeated
  until midnight of the next day.

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