Advanced Public Transit Systems (APTS)

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Advanced Public Transit Systems (APTS)

• Transit ITS

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APTS Products/Services

1. Service (Fleet) Management
2. Customer Information
3. Service Performance Monitoring
4. Vehicle Performance Monitoring
5. Incident Response
6. Wireless Communications

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APTS Products/Services

• Transit Signal Priority
• Collision Avoidance
• Fare Collection
• Connection Protection
• Demand-Response Routing and Scheduling
• Transit ITS Impacts Matrix
• http//web.mitretek.org/its/aptsmatrix.nsf

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Purpose of APTS

• Technologies used to provide Products/Services
  that address Problems related to
• Efficiency
• Reliability
• Safety
• Customer Satisfaction

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What would you change about transit service?
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Transit 101

• Fixed-Route Service (bus, rail)
• Established routes and stop sequences
• Scheduled time points
• Public timetables
• Block what a vehicle does for the day
• Block assignments change every day
• Run what a driver does for the day
• Run assignments change 3 or 4 times per year

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Transit 101 Continued

• Demand-Response Service (Dial-a-Ride,
  Paratransit)
• ADA Requirement
• Eligibility criteria
• Limited service area
• Usually reserve in advance
• Daily driver manifest

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More Transit 101

• Flex-Route Service
• Deviates from fixed route in response to demand
• Fixed end points and scheduled times

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APTS Building Blocks
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Smart Bus Components

• GPS Receiver
• On-board Computer
• On-board Network
• On-board Database
• Wireless Communication

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Transit Signal Priority(TSP)
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Transit Signal Priority (TSP)

• Problem Transit vehicles are slow
• Problem Transit vehicles are effected even more
  than cars by traffic lights
• The number of times you stop at traffic signals
  has a huge impact on travel time

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Transit Signal Priority

• Solution Give transit vehicles green lights on
  arterials
• Priority Versus Preemption (emergency vehicles)

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Transit Vehicle Priority

• Concerns with TSP
• Too much priority causes excessive side street
  delay
• Giving transit vehicles priority messes up
  progression
• Messed up progression slows buses even more
• Roadway agencies dont want to lose control of
  arterial

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Transit Signal Priority(TSP)

• Pre-emption

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Solution

• Find a graceful way of giving transit priority
• 1) Only change signal timing a little
• 2) Only change signal timing occasionally

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Change Signal Timing A Little

1. Hold the green just a little longer to get the
   bus through the intersection
2. Shorten the side street green time to get the
   green for the bus to occur more quickly
3. Use a new traffic signal algorithm

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Most Common Signal Logic Implementation

• Long Green or Short Red

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Only Change Signal Timing Occasionally

• What criteria do you use to determine which buses
  get priority?

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Only Change Signal Timing Occasionally

• Only late buses get priority
• Only special (Express?) buses get priority
• Only a few (random) buses get priority
• Priority is only available at some intersections
• Priority is only available on some corridors (bus
  priority corridors)
• Only full buses get priority

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Limited Timing Changes

• Each of these approaches has a different impact
  on the combination of
• Size of improvements to transit
• Size of impact to traffic
• Distribution of those improvements / impacts
• Amount of information needed to run the system

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TSP

• Lets examine how the TSP works

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TSP Basics

1. Identify bus as it approaches intersection
2. Determine if bus deserves priority
3. Determine if signal is willing to give priority
4. Determine if priority is needed (is signal green
   already?)
5. Change signal
6. Let signal return to normal operation

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Identify Approaching Bus

• Manual
• Will drivers use the system correctly?
• Automatic

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Identify Approaching Bus

• Beacon (signpost)
• GPS communications
• To central?
• To roadside?
• On-board dead reckoning
• With DSRC (dedicated short range communications)

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Determine if Priority Deserved

• Which buses get priority?
• If all buses easy
• If specific routes / runs need data transfer
• Transfer data to
• The bus
• The signal controller / interface
• A central location

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What Buses Get Priority?

• If only specific buses get priority, then there
  must be a connection between
• Vehicle ID,
• Daily Vehicle Assignment table (route/run),
• Route/run and signal cabinet location
• Maybe a priority table, and
• Clock

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What Buses Get Priority?

• Late Bus
• Requires Bus ID Route / Run
• Detailed knowledge of
• mid-point schedule times, and
• current location

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What Buses Get Priority?

• Only Full Buses
• Requires a current passenger count

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What Buses Get Priority?

• Limited number of buses
• Signal controller must keep track of
• How many priority calls have been given, or
• When was the last priority call made?

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Signal Controller Checks

• Is controller willing to give priority?
• Limits set by roadway agency
• Number of priority calls per hour
• Time required between calls
• Is priority needed?
• What phase is the controller currently in?

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Signal Controller

• If priority is permitted / needed
• Select appropriate action
• Hold green time
• Limit other green times
• No pedestrian calls
• Shorten side street green allowed
• Actuated signals
• Fixed time signals
• Other

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Let Signal Return to Normal

• The more quickly this happens the better
• Exit detection versus timing
• Timing is dependent on speed of the vehicle and
  location of detection zone

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Detection Zone Location

• Where is the bus stop?
• Advanced warning?
• Speed of processing (detection to priority call)
• Exit zone
• Reduces time taken from side streets

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Transit Signal Priority

• Puget Sound Regional Implementation

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Standard TSP Design

• Hardware
• AVI Tag Reader, or
• Transmitter receiver
• Interface with traffic signal controller
• Interfaces also with central for route/run
  priority information
• Extra readers to
• Give advance knowledge of bus approach
• Indicate bus has arrived at intersection
• Advise signal when bus has left intersection

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System Configuration
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TSP System Components
Tag
Interface Unit
Antenna
Reader Cabinet
Tag Interface Unit for Dynamic Data
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System Data Flow Diagram
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How and Why Do We Use TSP

• Keep buses on time
• Happy riders
• More riders?
• Speed up buses
• Happy riders
• More riders?
• Reduced transit cost (dont need to build in time
  to the schedule)
• Reduce variability in travel time
• Reduced transit cost (dont need to build in time
  to the schedule)
• Improves transfer timing (faster schedules?)

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Operating Strategies and TSP Benefits
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TSP Issues

• How much delay (mostly on side streets) does the
  priority system create?
• How many signal priority calls can be made?
• How much is exit detection worth?
• How do we control which buses get priority?
• What benefits do we get from TSP?
• How do we measure the benefits?

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TSP Issues

• Side Street Delay
• Effected by the type of priority calls
• Do we skip phases? Which phases?
• Do we shorten phases? Which phases? (peds?)
• Number of priority calls
• Size of side street versus priority direction
• Existing delay on side street

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TSP Issues

• How many calls can be made?
• Side street delay
• Effect of calls on progression
• How many calls actually change the signal timing?
• Can we monitor what actually happened?

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TSP Issues

• Is exit detection worth the cost?
• Importance of side street delay
• Cars
• Pedestrians
• Importance of cost
• (Note Light rail versus bus and the issue of
  throughput)

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Approximate TSP Costs per Approach

• Assumes underground installation
• Plus system engineering, integration, on-bus
  equipment

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TSP Issues

• What benefits do we get?
• Increased transit speed
• Increased transit reliability
• Both speed and reliability

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TSP Issues

• How do we measure the benefits / costs?
• Intersection delay?
• Vehicle delay
• Person delay (needs transit ridership)
• On time performance
• AVL / TSP calls / other
• Scheduled route time
• Bus schedules
• Requires feedback to the scheduling department

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TSP Issues - System Management

• Given all of the above choices, once the system
  is built
• How do we know it is working optimally?