ccat global symposium traffic optimization for signalized...

CCAT Global SymposiumTraffic Optimization for Signalized Corridors

27 February 2019

• This material is based upon work supported by the U.S. Department of Transportation under Cooperative Agreement No. DTFH6114H00002.

• Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the Author(s) and do not necessarily reflect the view of the U.S. Department of Transportation.

Acknowledgement and Disclaimer

02/27/2019CAMP – V2I Consortium Proprietary - Information contained in this document is considered work in progress subject to revision without notice. Content is provided “as is” solely for informational purposes with no express or implied

warranties that the information is up-to-date or complete. Use is solely at user’s own risk.2

• Traffic Optimization for Signalized Corridors (TOSCo)– A system that employs data transmitted via wireless communications from Roadside Units (RSU) to

connected vehicles to optimize vehicle fuel economy, emissions reduction and traffic mobility along a signalized corridor equipped to provide information required for TOSCo to operate

• The on-board application collects:– Signal Phase and Timing (SPaT)– Intersection geometry (SAE J2735 MAP Data Message, or MAP )– Essential information contained in the Roadside Safety Message (RSM)

• Employs V2I communications as well as data from nearby vehicles using Vehicle-to-Vehicle (V2V) communications

• The application performs calculations to determine the vehicle’s optimal speed to pass through one or more traffic signals on a green light or to decelerate to a stop and subsequently launch in the most performance-optimized manner

– Information is then sent to longitudinal vehicle control capabilities in the host vehicle to support partial automation.

Traffic Optimization for Signalized Corridors (TOSCo)



TOSCo System Architecture

BSM

OBU

TOSCoController

Brake / AccelActuators

CAN Data

←SPaT/MAP/ RSM / RTCM Data in→BSM Data out

Actuator Commands

Driver / Vehicle Interface

Driver Interaction

Data

SPaT/MAP/RSM/RTCM

RSE

Signal Controller

VehicleDetection

TOSCo Infrastructure

Algorithm

DetectorData

←SPaT/MAP/RSM/RTCM Data out

→BSM Data in

Constant Speed

Speed Up

CoordinatedStop Coordinated

Launch

Speed

DistanceFree-Flow

Out of Communication Range Free-FlowTOSCo Speed Control

Intersection Communication Range

CACCSet Speed

CACCSet Speed

Signal StatusVehicle Infrastructure

Slow Down

Stopped/Creep

BSM BSM BSM

BSM BSM BSMBSM

SPaT/MAP/RSM/RTCM



FREE_FLOW• Applies to all vehicles in a string• Vehicles operate in speed/gap control under CACC if TOSCo-equipped vehicles are

currently not receiving SPaT and MAP messages• Maps to Traffic Scenario #6COORDINATED_SPEED_CONTROL• Applies to Lead Vehicle in a string• Lead Vehicle employs SPaT / MAP / RSM message content to plan a speed profile

that allows it to pass through intersection by adjusting CACC set speed to achieve optimization objectives

• One of three possible speed profiles may be employed, depending on existingcircumstances:

– 1) slow down, maps to Traffic Scenario #1– 2) speed up, maps to Traffic Scenario #2– 3) maintain current speed, maps to Traffic Scenario #3

TOSCo Operating Modes



COORDINATED_STOP• Applies to Lead Vehicle in a string• Lead Vehicle employs SPaT / MAP / RSM message content to plan a speed profile

that allows it to come to a stop at the stop bar or end of a queue while meeting optimization objectives

• Maps to Traffic Scenario #4STOPPED• Applies to all vehicles in a string• TOSCo-equipped vehicle is stopped at the stop bar or in a queueCREEP• Applies to members of a string (preceding vehicle present)• TOSCo-equipped vehicle is allowed to creep forward toward the stop bar to fill

gaps left by vehicles that vacated lane during red phase– Example: Vehicle in right lane making a permissible right turn during a red phase




COORDINATED_LAUNCH• Applies to Lead Vehicle in a string• On-board system checks driver’s readiness for launch

– Checks whether driver has applied the brakes– System prompts the driver to release the brakes if applied

• System notifies driver of impending launch– Driver must respond to indicate readiness for launch otherwise the vehicle will not move– Applicable to all vehicles in the queue

• Lead Vehicle broadcasts a coordinated launch message as it launches upon transition to green phase

• Members of string wait for a Coordinated Launch message and launch upon reception of the message under OPTIMIZED_FOLLOW mode

• Maps to Traffic Scenario #5




OPTIMIZED_FOLLOW• Applies to members of a string• TOSCo-equipped vehicles operate predominately as a member of a string under

CACC speed and gap control– Continually receives SPaT / MAP / RSM messages to calculate optimized speed profile– May cause it to leave string and become lead vehicle in a new string if vehicle determines that

remaining in string will cause it to operate outside its range of optimized control

• Vehicle employs information from SPaT / MAP / RSM messages to determine whether it will be able to clear an approaching intersection before the next phase change

– Vehicle transitions to COORDINATED_STOP as lead vehicle in a newly formed string if it determines it will not clear the intersection in time remaining




• Plymouth Corridor (Ann Arbor, MI)

– 11 Intersections including two freeway interchanges covering about 4 miles– Speed limit variation: 35mph (west end) – 50mph (east end)– Shorter intersection spacing, more DSRC coverage– Terrain: mostly flat

Traffic-Level SimulationLow-Speed Corridor



Traffic-Level SimulationHigh-Speed Corridor

• 15 intersections between Montgomery, TX and Conroe, TX covering about 12 miles

• All the intersections are operated by the City of Conroe

• Posted speed limit range: 45 mph (east end) to 55 mph (west end)

• 55 mph for over 11 miles (less than 1 mi of east end is 45 mph)

Location of the signalized intersections considered along SH 105 (not yet equipped) Source: Google Maps

N



Infrastructure Algorithm

Traffic-level SimulationArchitecture

Traffic Simulator

Queue EstimatorDriverModel.dll

Emission.dll

ASC3 VirtualTraffic Controller SPaT Distributor

BSM

SPaT

SPaT, RSM

AccelerationCommand

VehicleTrajectory

SignalInfo SPaT

Vehicle Info

VISSIM

Detector Data

MAP and vehicle localization is implemented with VISSIM’s internal mechanism



• Mobility– Average Total Delay (s) (Per vehicle average)– Stop Delay (s) (Per vehicle average)– Queue Delay (s) (Per vehicle average)– Number of Stops (Per vehicle average)– Average Speed (km/h) (Total network)– Total Travel Time (hours) (Total network)

• Environment– Total energy (kJ / km) (Per vehicle average)– CO2 (gm / km) (Per vehicle average)– HC (gm / km) (Per vehicle average)– NOx (gm / km) (Per vehicle average)

Traffic-level SimulationPerformance Measures



Traffic-level SimulationLow-speed Network – Mobility

PR Tot. Delay Diff. (%) Stop Delay Diff. (%) # Stops Diff. (%)0% 109.78 69.45 1.48

10% 107.83 -1.78 67.12 -3.36 1.43 -3.2420% 108.75 -0.94 67.14 -3.33 1.44 -2.8430% 107.73 -1.87 66.05 -4.90 1.42 -3.9260% 106.39 -3.09 64.01 -7.84 1.39 -5.8190% 103.83 -5.43 61.76 -11.07 1.33 -9.86

100% 102.72 -6.43 60.61 -12.73 1.32 -10.68

01234

50

75

100

125

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Aver

age

Num

ber o

f Sto

p (#

/veh

)

Aver

age

Dela

ys (s

/veh

)

Penetration Rates

Mobility Measurements (Network)

Average Total Delay Average Stop Delay Number of Stops



Traffic-level SimulationLow-speed Network - Environment

PRCO2 Emission

(gm/km) Diff. (%)Total Energy

(KJ/km) Diff. (%)0% 185.34 2552.95

10% 184.16 -0.64 2536.58 -0.6420% 184.09 -0.68 2535.66 -0.6830% 183.11 -1.21 2522.14 -1.2160% 180.81 -2.45 2490.51 -2.4590% 178.20 -3.85 2454.60 -3.85

100% 177.21 -4.39 2440.86 -4.39

3500

3700

3900

4100

4300

4500

250

270

290

310

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Tota

l Ene

rgy

(Kj/m

ile)

CO2

Emiss

ion

(g/m

ile)

Market Penetration

CO2 and Total Energy Measurements (Network)

CO2 Total Energy



• TOSCo can smooth vehicle trajectories to bring fuel benefit• TOSCo is more effective at higher delay intersections with under-saturated

traffic conditions– Higher volume and/or poor signal coordination

• Lower delay intersections (e.g., low demand, good signal progression) result in less opportunity for TOSCo operation to make an impact

• TOSCo strings– Increases capacity and reduces delay– But, potential to block lane changes due to smaller headways

• Overall– TOSCo brings mobility benefits: total delay, stop delay, # stops, average speed,

total travel time– TOSCo brings environment benefits: total energy, CO2, HC and NOx

Traffic-level SimulationLow-speed Network – Observations



• TOSCo has demonstrated smoother traffic flow especially at higher penetration rates– Coordinated launch has significant positive impact in discharging queues of

TOSCo-equipped vehicles

– Vehicles adjust speed earlier to match green window

– Improvements more visible with greater penetration rate (>60%)

– Stop delay significantly reduced

– TOSCo vehicles maintain motion which improves fuel economy / emissions reduction

• Maximum TOSCo benefit would be achieved over the length of an equipped corridor– Benefits are cumulative over a series of intersections

Traffic-level SimulationHigh-speed Network – Observations



Project Next Steps

• Define preliminary deployment guidelines for corridors where TOSCo would have a positive impact– Examine minimum volume thresholds to provide

“predictability” of green window– Examine maximum volume thresholds to limit likelihood

of queues not clearing before TOSCo vehicle arrival– Probability of string size at various v/c ratios

• Conduct closed course and public road testing



Thank you

Traffic Optimization for Signalized Corridors (TOSCo)



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