ATMS

1. ATMS Advanced Traffic Management Systems

2. ATMS • Intent of ATMS: • Improve operational control • Adapt control strategies to current/expected traffic • Provide marginal improvements to system capacity or throughput • Reduce congestion / delay / queues

3. ATMS Requires • Control mechanism • Surveillance function • Communications • Data manipulation • Control algorithm • Maintenance function

4. ATMS Requires • Control mechanism • Stop lights • Barriers • Traveler information? • How DO you control trafficon a “freeway”?

5. ATMS Requires • Surveillance function • Loops • Cameras • As data • As images • Other • Radar • Vehicle probe data

6. ATMS Requires • Communications • To obtain the surveillance data, and • Request required control system changes

7. ATMS Requires • Data manipulation • What exactly do you do with the data you have? • Decision support systems • Data fusion • Using data from multiple sensors

8. ATMS Requires • Control algorithms • Old • Time of day • Fixed volumes • New • Adaptive • Real time volumes • Predictive (in time or space)

9. ATMS Requires • Maintenance of the system • Operational systems need a higher level of maintenance than simple infrastructure • Fail safe operational requirements • How much data is enough? • 1 of 4 lanes? • What spacing of detection?)

10. ATMS Requires (?) • Optional functions • data collection • storage, and • performance monitoring / operations planning

12. Examples of ATMS • Freeway systems • Ramp metering • Fixed time • Local adaptive • System level adaptive control • Routing • Adaptive speed control

13. Examples of ATMS • Arterials Control Systems • Actuated & semi-actuated control • SCOOT • SCATS • OPAC • RT-TRACS • (NSATMS) • RHODES

14. Examples of ATMS • Automated toll collection • Parking systems • Emergency response

15. Ramp Metering • Objectives: • Reduce conflicts at ramp terminals • Decrease merge congestion • Reduce accident rates • Encourage diversion to/from specific ramps • Limit total volume on specific freeway segments at specific times

16. Ramp Metering • Objective: Maintain flow at maximum levels by • Preventing flow break down • Increase total hourly throughput by maintaining throughput • Improve speed of incident recovery • Promote/deny specific movements

17. Ramp Metering • Minimize air pollution emissions and gasoline consumption by reducing stop and start movements • Minimize ramp delays while maintaining mainline flow • Minimize queue spillback onto arterials

18. Ramp Metering Maximize freeway flow and freeway performance is contradictory to Minimize ramp queues and ramp delays

20. Ramp Metering • Keys to successful operation • Know the maximum volume that can use each ramp • Current local mainline volume • Future local mainline volume (upstream volume) • Downstream congestion • Finding the correct balance between ramp queue and freeway delay

21. Ramp Metering • Know the Volume • Needs surveillance • On the mainline • Approaching the merge point • Upstream of the merge • Downstream of the merge • By the stop bar on the ramps • Queue length • Advanced queue detection

23. Ramp Metering • Bring the data back to a central point • This allows decisions to be made given geographic areas larger than “locally” • Also allows data storage for later review / analysis

24. Ramp Metering • Local control • minimize merge conflict • Bottleneck algorithm • maximize ramp queue, given no current downstream freeway delay • Fuzzy Neural Network • trade off ramp queues against mainline flow • avoids direct use of volume

25. Freeway ATMS – Route Control • Move vehicles to those routes with spare capacity • Operational concerns • Are there parallel routes with spare capacity? • Are there routes (ramps) where merging causes less disruption? • Will the diversion cause more congestion than it will relieve?

26. Freeway ATMS – Route Control • Route Diversion • Political concerns - what are the impacts of route diversion? • Are the new routes designed for that traffic? • Are there concerns about who benefits / loses? • Do the people/businesses that live along those routes object to their use by “pass through” traffic?

27. Freeway ATMS – Route Control • Technical – How do you cause drivers to divert? What route do they take? • Traveler information (VMS / CMS / HAR / radio) • Metering (fast versus slow) • Ramp closures • New technology (PDA messages) • Can you manage how many vehicle change routes? • Many drivers won’t change routes

28. Surveillance

29. Surveillance • Is necessary to manage traffic • Without surveillance, there is no knowledge of what is occurring

30. Surveillance Technologies • Loops • Cameras • Other technologies • Radar • Acoustic • Infrared • Other

31. Inductance Loop

32. Loops • Advantages • Inexpensive • Easy to install • Well known attributes / mechanics • Provide • Volume • Lane occupancy • Speed (sometimes) • Vehicle classification

33. Loops • Disadvantages • Single location (non-movable) • Subject to pavement failure / degradation • Not good if channelization is likely to change • Difficult to collect vehicle classification data • Dual loops • Inductance signature recognition

34. Cameras • Two basic technologies • Video • Digital image processing

35. Pan/Tilt/Zoom Camera

36. Cameras • Conventional video • Needs a person watching • Great for short time period • Poor for longer time periods • Good for incident verification • Good for public information • Not good for routine data collection

37. Cameras • Digital Image Processing • Reasonably new technology (+15 years at a reasonable price) • Several different technologies • Each with different costs / capabilities

38. Cameras • Autoscope - style • A US vendor – early adopter • Uses low cost, fixed cameras • Acts like a digital loop • Has limitations in bad weather / lighting

39. Cameras • Other digital image processing • Movable cameras • Harder to calibrate • More expensive cameras • Multi-use cameras • Vehicle tracking systems • Travel times • License plate readers

40. Other Technologies • Radar • Side fired / Over-head mounted • Data similar to loops • A non-intrusive sensor (easier to access) • Acoustic • Also a non-intrusive sensor

41. Other Technologies • Infrared • Both with reflector and without reflector • Non-intrusive • Not effected by weather • Other • RF for electronic tag reading • Surface acoustic wave (SAW) for tag reading • Optical scanners (bar codes)

42. Other Technologies • http://www.nmsu.edu/~traffic/ • Summary of Vehicle Detection and Surveillance Technologies Used in Intelligent Transportation Systems - Detector Handbook (under What’s New)

43. Surveillance • When choosing surveillance system / technology • Type of data collected • Cost of data collection • Accuracy of data collected • Reliability of equipment • Frequency of communications • Flexibility

44. Type of Data • Volume • Vehicle presence • Lane occupancy • Vehicle classification • Vehicle speed / travel time • Weight • ID • Other (location? status? revenue?)

45. Cost of System • Purchase • Installation • Operation • Maintenance

46. Cost • Purchase price • Sensor • Electronics • Communications • Software • License? (How many can you use?)

47. Cost • Installation location effects cost • In ground • Below ground • Pole mounted • Bridge mounted • Need for traffic control? • Communications • Power • Cabinets

48. Cost • Operations • Power • Communications • Bandwidth required • Wireless / wireline • Frequency of communications • Staff oversight

49. Cost • Maintenance • Mean time before failure (life cycle costs) • Routine maintenance requirements • External effects • Bad weather • Deteriorated pavement conditions • Replacement parts (sole source?) • Ease of sensor replacement

50. Accuracy • How important is it? • Can you accept small errors? • Volume +5% • Speed + 3 mph • Error in reading Toll tags? • Classification of truck • It depends