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Advance Preemption Costs More than Simultaneous Preemption: Fact or Fiction?. Typical RR Preempted Intersection. Intersection Phasing. Phase 6. Phase 1. 8 Ped. Phase 8. Phase 3. 2 Ped. 6 Ped. Phase 7. Phase 4. 4 Ped. Phase 5. Phase 2. MUTCD / AREMA Definition. - PowerPoint PPT Presentation
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Advance Preemption Costs More than Simultaneous Preemption:
Fact or Fiction?
Typical RR Preempted
Intersection
8 Ped
2 Pe
d6 Ped4 Ped
Phase 4Phase 7
Phas
e 6
Phase 3
Phas
e 5
Phase 8
Phas
e 1
Phas
e 2
Intersection Phasing
MUTCD / AREMA Definition
Maximum Preemption Time
The maximum amount of time needed following initiation of the preemption sequence for the highway traffic signals to complete the timing of right-of-way transfer time, queue clearance time, and separation time.
MPT = RWTT + QCT + ST
MUTCD / AREMA Definition
Right-of-Way Transfer Time (RWTT)
The maximum amount of time needed for the worst case condition, prior to display of the track clearance green interval. This includes any railroad or highway traffic signal control equipment time to react to a preemption call, and any traffic control signal green, pedestrian walk and clearance, yellow change, and red clearance intervals for conflicting traffic.
Receive Preemption Request• Phase 2 Minimum Green (7 seconds)• Phase 2 WALK (7 seconds)
Right-of-Way Transfer Time• Phase 2 Minimum Green (7 seconds)• Phase 2 Pedestrian Change (23 seconds)
Right-of-Way Transfer Time• Phase 2 Yellow Change (4 seconds)
Right-of-Way Transfer Time• Phase 2 Red Clearance (2 seconds)
Right-of-Way Transfer Time
WALK 0 seconds
Flashing DONT WALK 23 seconds
YELLOW Change 4 seconds
RED Clearance 2 seconds
TOTAL Right-of-Way Transfer 29 seconds
MUTCD / AREMA Definition
Queue Clearance Time (QCT)
The time required for the design vehicle of maximum length stopped just inside the minimum track clearance distance to start up and move through and clear the entire minimum track clearance distance.
Minimum Track Clearance Distance (MTCD)
The length along a highway at one or more railroad tracks, measured either from the highway stop line, warning device, or 12 ft perpendicular to the track centerline, to 6 ft beyond the track(s) measured perpendicular to the far rail, along the centerline or edge line of the highway, as appropriate, to obtain the longer distance.
MTCD
Clear Storage Distance (CSD)
The distance available for vehicle storage measured between 6 ft from the rail nearest the intersection to the intersection stop line or the normal stopping point of the highway.
CSD
Queue Start-up Distance (L)
The maximum length over which a queue of vehicles stopped for a red signal indication at an intersection downstream of the crossing must get in motion so that the design vehicle can move out of the railroad crossing prior to the train’s arrival. The sum of CSD and MTCD.
MTCD CSD
L
MTCD
Queue Clearance Distances
CSD
L
Design VehicleThe longest vehicle permitted by statute of the road authority (State or other) on that roadway.
Maybe even longer….Double or Triple Trailer ?
55’
65’
Why do we need to clear the tracks? Everybody knows not to stop on the tracks. There’s
even a sign.
Queue Clearance (First Component)Queue Start-up – Time elapsed after beginning of track clearance green until design vehicle can start moving. All red vehicles must move before design vehicle (yellow truck) can begin to accelerate.
Queue Clearance (Second Component)Design Vehicle Clearance – Time required for design vehicle to accelerate from a stop and travel through and clear of MTCD.
Queue Clearance Time
Queue Start-up Time before design vehicle begins to moveCalculate as 2 + (L/20)
6 seconds
Design Vehicle ClearanceTime for design vehicle to accelerate through design vehicle length and MTCD
14seconds
TOTAL Queue Clearance 20 seconds
MUTCD / AREMA Definition
Separation Time (ST)
The component of maximum highway traffic signal preemption time during which the minimum track clearance distance is clear of vehicular traffic prior to the arrival of the train.
Separation TimeDesign vehicle allowed to move more than 6 ft clear of MTCD prior to train arrival.
4 sec ST
Train Arrival
Maximum Preemption Time
Right-of-Way Transfer Time 29 seconds
Queue Clearance Time 20 seconds
Separation Time 4 seconds
TOTAL Max Preemption Time 53 seconds
RR Warning Times
Simultaneous Preemption Set RR Minimum Warning Time equal to Maximum Preemption Time.
MWT = MPT
Advance PreemptionSet Advance Preemption Time equal to Maximum Preemption Time minus RR Minimum Warning Time
MWT = 20 APT = MPT - 20
RR Warning Times
Simultaneous PreemptionMinimum Time 20
Clearance Time 33
Buffer Time 5
Equipment Response 5
Advance Preemption 0
Total Approach Time 63
Advance PreemptionMinimum Time 20
Clearance Time 0
Buffer Time 5
Equipment Response 5
Advance Preemption 33
Total Approach Time 63
Total Approach Time is the SAME !
Time Line Comparison29 Second RWTT
Things That Do Affect Cost
Right-of-Way Transfer Time• Minimum Green (engineering judgment)• Walk (omit or shorten permitted by MUTCD)• Pedestrian Change (omit or shorten permitted
by MUTCD)
Time Line Comparison11 Second RWTT
Things That Do Affect Cost
Vehicle – Gate Interaction Check• Additional Advance Preemption Time to keep
gate from striking design vehicle
Time Line Comparison29 Second RWTT with VGI
Time Line Comparison11 Second RWTT with VGI
