ARE YOU ADAPTIVE? (From a Traffic Signal Perspective)

Transcription

1 ARE YOU ADAPTIVE? (From a Traffic Signal Perspective)

2 ADAPTIVE TRAFFIC CONTROL SYSTEMS (ATCS) What are they? How are they different from other ATMS (especially traffic responsive)? Is it right for my jurisdiction?

3 EARLY SYSTEMS Split-Cycle-Offset Optimization Technique (SCOOT 1981) Sydney Coordinated Adaptive Traffic System (SCATS 1982)

4 RESPONSIVE vs. ADAPTIVE What s the difference? Traffic responsive has pre-determined timing plans. When running traffic-responsive, the ATMS picks one of the patterns based on signature values of volume, speed and density. ATCS generally don t have cycle length and offset constraints, but have mathematical programs that determine signal operation.

5 POTENTIAL PROS and CONS Primary Advantages: Don t require constant re-timing with volume changes. Reacts better to unpredictable volume demands. Primary Disadvantages: More extensive detection system (more costly to install and maintain). Black box operation (not sure what it s doing).

6 TRAFFIC ADAPTIVE in ARIZONA RHODES Developed at the University of Arizona Tempe: tested at two locations Tucson: tested at 15 intersections SCATS To be installed in Mesa this year

7 ATC SYSTEMS SCOOT (Split Cycle Offset Optimization Technique) SCATS (Sydney Coord. Adaptive Traffic System) OPAC (Optimization Policies for Adaptive Control) UTOPIA (Urb. Traffic Opt. by Integrated Automation) ACS Lite (Adaptive Control Software) RHODES (Real-time Heirarchical Opt. Distrib. & Eff. Sys.) L.A. DOT ATCS BALANCE MOTION InSync

8 ATCS OPERATIONAL CHARACTERISTICS Arterial networks (e.g., ACS Lite and SCATS) vs. grid networks (e.g., SCOOT and UTOPIA) Identifiable operational elements: Detection Type of action Adjustment method and time frame Signal timing adjustments Ability to form regions Support for vehicle-actuated operations Transit operations

9 DETECTION Four major types: Stop-line Near-stop line Upstream/mid-block Upstream/far-side Form of detection: 93% of ATCS users rely on loops, although 43% of them also use video ATCS generally require more coverage than typical traffic-actuated signal systems

10 TYPE of ACTION Proactive ATCS Adjust to meet estimated demands Likely to use upstream detectors Reliance on modeling Reactive ATCS Use previous data logs to adjust Likely to use stop-line detectors Inherently delayed in making adjustments

11 SIGNAL TIMING ADJUSTMENTS Green splits Cycle lengths Offsets A few adjust or optimize phase sequencing in real-time (BALANCE, MOTION, and InSync)

12 ADJUSTMENT METHOD and TIME FRAME Domain-constrained optimization To avoid high fluctuations of timings Time-constrained optimization Set by local controller policies Rule-based adjustment Simple functional relationship between parameters concerning changing traffic conditions and resulting timings Parameter adjustments range from every few seconds to every 10 to 15 minutes

13 FLEXIBILITY to FORM REGIONS Some require entire coverage area to be divided into regions/subsystems for coordination (SCOOT, SCATS, and LA ATCS) SCATS marriage and divorce logic supports automatic reconfiguration of the subsystems based on given criteria

14 SUPPORT for VEHICLE- ACTUATED OPERATIONS How are gap-out operations executed? ATCS initiated or local controller initiated RHODES does not allow a local controller to execute these decisions SCATS, BALANCE, MOTION, and ACS Lite will allow local controller execution of its gap-out logic

15 TRANSIT SIGNAL PRIORITY Most ATC Systems presented provide some type of transit vehicle priority Priority is often provided at the local controller s level

16 CHARACTERIZATION SUMMARY ACS Lite BALANCE InSync LA ATCS MOTION OPAC RHODES SCATS SCOOT UTOPIA Detection SL, MB/US NSL NSL SL & US NSL SL & MB SL & MB SL, NSL, MB SL & US SL & US Action Pro/React Pro/React Pro/React Pro/React Pro/React Pro Pro React Pro/React Pro Adjustment Domain Time Domain All Time Time Time Rule Domain Time Time Frame 5-10 min 5 min Ph/CL/ 15-min CL 5-15 min Ph/CL/ 5-min Ea. Sec CL CL/5-min 3 sec/cl Timings S/O S/CL/O/PS S/CL/O/PS S/CL/O S/CL/O/PS S/CL/O S S/CL/O S/CL/O/PS S/PS Flex Region No No Yes Yes No No No Yes Yes Yes Veh-Actuated Yes Yes No Yes Yes No No Yes Yes Yes TSP No Yes Yes Yes Yes Yes Yes Yes Yes Yes

17 BENEFITS of ATCS Commitment to staffing and maintenance (with higher expertise) in order to best realize benefits ATCS users: 10 to 30% signals part of ATC System ATCS users recognize the following as most important benefits: Good response to emergency vehicle preemption, congestion from crashes, fast clearing Typical fluctuations in demand, fast response Does better when traffic flow is incremental, not volatile Maximized throughput Ease of network control

18 BENEFITS of ATCS (cont.) Limited field evaluation studies pertaining to benefits from fine-tuning of an existing ATCS deployment Individual user benefits vs. traveling public (20% to 35% improvement in typical MOEs) 71% of users evaluations reported ATCS as outperforming conventional traffic signal systems Most agencies (70%) have expanded their systems since initial installation. Benefits not observable in over-saturated conditions

19 COSTS Licensing costs are typically only 10% to 15% of the overall installation costs Survey of ATCS users shows average installation cost per intersection is $65,000 (most at $40,000) within a range of $20k to $70k+ ATCSs found to only require 75%, on average, of the typical funding to maintain non-atcs systems at optimal timings

20 GUIDELINES / LESSONS LEARNED Better local support from the vendor Better planning for in-house support Good preparation of the infrastructure (detection and communications) Detailed pre-installation evaluation to facilitate estimation of operational benefits No in-depth investigation of factors that represent barriers for new deployments

21 HOW DOES an AGENCY DECIDE WHAT KIND of ATMS? All ATMS are expensive and (hopefully) will be in use for years. Develop an evaluation process (feasibility study) conventional ATMS or ATCS? Factors to consider: volume fluctuations; available staff for retiming; cost Prioritize needs and goals of all stakeholders Constant-Sum paired comparison Consider procurement typical low bid process doesn t work well for ATMS

22 Questions?