Advanced Persistent Threats (APTs) Subversive Multi-Vector Threats
Advanced Public Transit Systems (APTS) Transit ITS CEE582.
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Transcript of Advanced Public Transit Systems (APTS) Transit ITS CEE582.
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
7. Transit Signal Priority
8. Collision Avoidance
9. Fare Collection
10. Connection Protection
11. Demand-Response Routing and Scheduling
Transit ITS Impacts Matrixhttp://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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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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Base Map (GIS)
Routes & Stops
Schedules
Vehicle Location (AVL)
Passenger Information
Base Map (GIS)
Routes & Stops
Schedules
Vehicle Location (AVL)
Passenger Information
“Smart Bus” Components
• GPS Receiver
• On-board Computer
• On-board Network
• On-board Database
• Wireless Communication
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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
Transit Signal Priority
• Solution: Give transit vehicles green lights on arterials
• Priority Versus Preemption (emergency vehicles)
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 don’t want to lose control of
arterial
Solution
Find a graceful way of giving transit priority
1) Only change signal timing a little
2) Only change signal timing occasionally
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
Only Change Signal Timing Occasionally
• What criteria do you use to determine which buses get priority?
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
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
TSP Basics
1) Identify bus as it approaches intersection2) Determine if bus deserves priority3) Determine if signal is willing to give
priority4) Determine if priority is needed (is signal
green already?)5) Change signal6) Let signal return to normal operation
Identify Approaching Bus
• Beacon (signpost)
• GPS + communications– To central?– To roadside?
• On-board dead reckoning– With DSRC (dedicated short range
communications)
Determine if Priority Deserved
1) Which buses get priority?• If all buses = easy• If specific routes / runs = need data transfer
2) Transfer data to• The bus• The signal controller / interface• A central location
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
What Buses Get Priority?
• Late Bus
• Requires Bus ID + Route / Run +
• Detailed knowledge of – mid-point schedule times, and – current location
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?
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?
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
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
Advanced Detection
Exit Detection
Presence Detection
Signal Controller and Interrogator
Mainline Signal
Bus Detector
Intersection
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
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
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 (don’t need to build in time to the
schedule)
• Reduce variability in travel time– Reduced transit cost (don’t need to build in time to the
schedule)– Improves transfer timing (faster schedules?)
H ighcustom er
benefit
Lowcustom er
benefit
Low financia lbenefit
H igh financia lbenefit
S trategy A(fewer stops)
S trategy D(im proved on-
tim eperform ance)
S trategy C(consistently
faster average busspeeds and/or
consistently lessvariab le travel
tim es)
S trategy B (ocassionalfaster express service)
Operating Strategies and TSP Benefits
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?
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
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?
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)
Approximate TSP Costs per Approach
• Assumes underground installation• Plus system engineering, integration, & on-bus equipment
Without Exit Detection With Exit Detection
Design $2,400 $2,400Construction* $6,000 $7,000Reader Hardware $8,000 $16,000Controller/Interface $5,000 $5,000
$21,400 $30,400
TSP Issues
• What benefits do we get?– Increased transit speed– Increased transit reliability– Both speed and reliability
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