1. Nick Wood, P.E. Texas A&M Transportation Institute
Application of the Traffic Thermostat for the I-30 Managed Lanes in Dallas, TX
Nick Wood, P.E.
Texas A&M Transportation Institute
Monday, May 15th, 2017
16th TRB National Transportation Planning Applications Conference
Raleigh, North Carolina

2. Overview Managed lanes is an umbrella term for Variety of goals
“highway facilities or a set of lanes where operational strategies are proactively implemented and managed in response to changing conditions”
Variety of goals
Person throughput
Vehicle throughput
Ensure reliability
Increase transit ridership
Increase carpooling
Increase revenue generation
Set of operational strategies
Restrict access to carpools
Variable tolling
Change transit headways
Rideshare incentives
Alter physical access points
Traffic control (reversible flow)
TRB Speed Paper (NCHRP 15-49)

3. Problem Lifecycle performance management is difficult Example
Long-term changes in demand, shifts in travel behavior
Example
Two-person HOV lane with high demand, slowed speeds, and unreliable conditions
Can increase occupancy to HOV3+, but most users are HOV2
TRB Speed Paper (NCHRP 15-49)

4. Traffic thermostat tool
Guides planners through a series of steps and questions
Evaluate strategies given predetermined performance
Helps to ensure mobility pledge with travelers
If facility degrades, series of pre-selected strategies are enacted until performance thresholds are met
Modification for specific facility and behavioral characteristics
Goal: Have MPOs approve an operational framework before onset of degraded performance
TRB Speed Paper (NCHRP 15-49)

5. Identify Facility Type Operational Fixes, Adjust Incentives
Thermostat Steps 1
Identify Facility Type 2
Set Goals 3
Set Thresholds 4
Rank User Groups 5
Operational Fixes, Adjust Incentives
RESULTS
TRB Speed Paper (NCHRP 15-49)

6. Example: I-30 Managed Lanes
Conversion from existing HOV to HOT lane
Extends for 18 miles from Arlington to Dallas, Texas
First section opened August 1, 2016
Addition of tolls
First 6 months: Tolls change according to a time-of-day schedule
After: Tolls become dynamic, according to demand
Prices range from $0.43 to $1.14 per mile
HOV2+ receive 50% toll discount during peaks when mobile app declares occupancy
Strong emphasis on TDM programs
TRB Speed Paper (NCHRP 15-49)

7. Tool Modifications Demand elasticities Volume-delay function
Derived from a stated preference survey
General price elasticity was -0.3
Volume-delay function
Integrated from regional travel demand model to help estimate speed and throughput
Conical congestion delay estimated given hourly link volume and capacity for general purpose lanes (GPLs) and managed lanes (MLs)
Incentive
Mode
Calculated Elasticity
MLDA Inc1
GPL
−0.050
MLDA
0.243
MLCP
Transit
MLCP Inc1
−0.039
0.254
MLDA Inc2
0.003
−0.018
MLCP Inc2
0.002
−0.019
MLDA Inc3
−0.024
0.129
MLCP Inc3
0.135
Transit Inc4
−0.073
Transit Inc5
−0.017
0.366
Transit Inc6 (% change only)
−1.1
33.1
TRB Speed Paper (NCHRP 15-49)

8. Step 1: Identify Facility Type
Identified from a list of pre-determined types
HOV (High-Occupancy Vehicle) Lanes
Travel permitted for carpools and other select groups
HOT (High-Occupancy Toll) Lanes
Some groups travel free, others pay a toll
Toll Lanes
All drivers pay a toll
The I-30 Managed Lanes are HOT Lanes
HOT Lanes
TRB Speed Paper (NCHRP 15-49)

9. Step 2: Set Goals
Select from list of pre-defined goals and performance metrics
Safe Travel
Metrics: Number of Crashes, Incident Clearance Time
High-Speed Travel
Metrics: Average Speed, Travel Time
Reliable Travel
Metrics: Buffer Index, Days per month below threshold
Provide Choice
Metrics: Perception of User Choice, Number of Unique Users
Maximize Throughput
Metrics: Person Throughput, Person Throughput in HOVs
Selected Goals: High-Speed Travel and Maximize Throughput
TRB Speed Paper (NCHRP 15-49)

10. Step 3: Set Thresholds Each metric set for a specific numeric value
Average Speed > 50 mph
Based on pre-approved regional goals for ML facilities
Person Throughput > 5,700 people per hour
Based on assumptions for vehicular volume and average occupancy
TRB Speed Paper (NCHRP 15-49)

11. Step 4: Rank User Groups Distinct user groups ranked according to:
Prioritization = highest
Toll status free, tolled, not allowed
TRB Speed Paper (NCHRP 15-49)

12. Step 5: Operational Fixes And Incentives
TRB Speed Paper (NCHRP 15-49)

13. Step 5: Operational Fixes And Incentives
TRB Speed Paper (NCHRP 15-49)

14. Results Screen Initial Condition (Travel Speed = 48 mph)
Vehicle Group Volume Type Priority Toll ($)
HOV Tolled 3 2
HOV Tolled 4 2
SOVs 2300 Tolled 5 4
Motorcycles 30 Tolled 3 2
Transit 10 Free 1 0
Vanpools 8 Free 2 0
Other Buses 5 Free 2 0
Resultant (Estimated Travel Speed = 51 mph)
Vehicle Group Volume Type Priority Toll ($)
HOV Tolled 3 2
HOV2 991 Tolled 4 2
SOVs 2006 Tolled 5 6
Motorcycles 30 Tolled 3 3
Transit 14 Free 1 0
Vanpools 8 Free 2 0
Other Buses 5 Free 2 0
TRB Speed Paper (NCHRP 15-49)

15. Key Findings Thermostat is a challenge due to
Conflicting goals, such as increased throughput and high-speed travel
Swapping fixes and incentives requires user to go back-and-forth, which may be difficult to track
Big Picture: shows the inherit difficulty
Obtaining necessary data
Understanding traffic relationships
Assessing impact of operational fixes and incentives
TRB Speed Paper (NCHRP 15-49)

16. More Information Website link: http://trafficthermostat.tti.tamu.edu/
Work will be published in the Transportation Research Record later this year Vol. 2616, DOI: /
Contact Info:
Nick Wood, P.E.
Texas A&M Transportation Institute
Phone:
TRB Speed Paper (NCHRP 15-49)