Transcript 2012 Minnesota DOT – ACEC Annual Consultant Conference

2012 Minnesota DOT – ACEC Annual Consultant Conference
Alternatives to Advanced
Preemption at Railroad
Crossings
2012 Minnesota DOT – ACEC Annual Consultant Conference
What is Railroad Preemption at a
Grade Crossing?
2012 Minnesota DOT – ACEC Annual Consultant Conference
Railroad Preemption:
A special control mode in a traffic signal controller
designed to start up and clear any vehicular
traffic on the roadway approach crossing the
railroad tracks
Then allows only traffic movements that do not
conflict with the railroad for the duration of the
train movement
2012 Minnesota DOT – ACEC Annual Consultant Conference
1. Terminate any
allowable
combination of
phases and
associated
pedestrian
movements.
8 3
2
5
1
6
7 4
2012 Minnesota DOT – ACEC Annual Consultant Conference
2. Display Green
for Track
Clearance
Movements
and hold in
Green until
railroad gates
are down.
8 3
2
5
1
6
7 4
2012 Minnesota DOT – ACEC Annual Consultant Conference
3. Allow only
those phases or
movements
that do not
conflict with
crossing until
preemption
ends.
8 3
2
5
1
6
7 4
2012 Minnesota DOT – ACEC Annual Consultant Conference
3. Allow only
those phases or
movements
that do not
conflict with
crossing until
preemption
ends.
8 3
2
5
1
6
7 4
2012 Minnesota DOT – ACEC Annual Consultant Conference
3. Allow only
those phases or
movements
that do not
conflict with
crossing until
preemption
ends.
8 3
2
5
1
6
7 4
2012 Minnesota DOT – ACEC Annual Consultant Conference
What is Advanced
Preemption?
2012 Minnesota DOT – ACEC Annual Consultant Conference
Advanced Preemption is an
operating mode which allows the
traffic signal to display green to
clear the track before the railroad
flashing lights begin to operate
2012 Minnesota DOT – ACEC Annual Consultant Conference
1. Track
clearance
green interval
begins
8 3
2
5
1
6
7 4
2012 Minnesota DOT – ACEC Annual Consultant Conference
2. Railroad
warning
devices begin
to operate
8 3
2
5
1
6
R
G
IL
R
O
D
7 4
G
IL
O
SS
IN
RA
R
A
C
C
R
O
SS
IN
A
RO
AD
2012 Minnesota DOT – ACEC Annual Consultant Conference
3. End track
clearance
green
8 3
2
5
1
6
R
G
IL
R
O
D
7 4
G
IL
O
SS
IN
RA
R
A
C
C
R
O
SS
IN
A
RO
AD
2012 Minnesota DOT – ACEC Annual Consultant Conference
That seems simple enough, what’s
the issue here?
2012 Minnesota DOT – ACEC Annual Consultant Conference
When preemption is implemented,
adequate time must be provided
in order to permit a Design Vehicle
to clear the crossing prior to the
arrival of the train
75’ in MN
2012 Minnesota DOT – ACEC Annual Consultant Conference
So how much
time does it take
for preemption to
operate?
101’
In this example,
52 seconds is
required.
2012 Minnesota DOT – ACEC Annual Consultant Conference
Minimum Green = 7 seconds
Pedestrian Change = 29 seconds
Yellow Change = 4 seconds
Red Clearance = 2 seconds
32 seconds of Advanced Preemption Time
required at this location
2012 Minnesota DOT – ACEC Annual Consultant Conference
The required
amount of time
must be provided
by the railroad
train detection
circuitry
2012 Minnesota DOT – ACEC Annual Consultant Conference
MUTCD requires
that the railroad
must provide a
minimum 20
seconds of
warning prior to
the arrival of a
through train
2012 Minnesota DOT – ACEC Annual Consultant Conference
Any time required
beyond the
minimum warning
time prior to the
arrival of a train
becomes an
addition to a basic
warning system
project
2012 Minnesota DOT – ACEC Annual Consultant Conference
In a nutshell..
Time
=
$$$
2012 Minnesota DOT – ACEC Annual Consultant Conference
Why?
1. Substantial additional circuitry due to
electrical design limitations of the train
detection equipment
2. Railroad train control signal system must
co-exist with crossing systems
3. Remote equipment locations which may
be 1000’s of feet from the crossing
4. Extensive underground cabling to remote
locations
2012 Minnesota DOT – ACEC Annual Consultant Conference
What are the alternatives to
advanced preemption or lengthy
advanced preemption times?
2012 Minnesota DOT – ACEC Annual Consultant Conference
Turn off
the traffic
signal
Effective?
Practical?
2012 Minnesota DOT – ACEC Annual Consultant Conference
Grade
Separate
the
Crossing
Even more
$$$
2012 Minnesota DOT – ACEC Annual Consultant Conference
Close the
Crossing
Never a
popular
choice with
local
politicians
2012 Minnesota DOT – ACEC Annual Consultant Conference
Practical Engineering Solutions
2012 Minnesota DOT – ACEC Annual Consultant Conference
Pedestrian Treatments
Crosswalk Elimination
2012 Minnesota DOT – ACEC Annual Consultant Conference
From our example, the Pedestrian
Change Time is 29 seconds
Engineering changes to the
intersection can reduce the time
required from the railroad
2012 Minnesota DOT – ACEC Annual Consultant Conference
In many cases,
there is no
sidewalk present
between the track
and the parallel
roadway
2012 Minnesota DOT – ACEC Annual Consultant Conference
Eliminate the
crosswalk parallel
and closest to the
track
Can save 2 – 4
seconds of
pedestrian
change time
2012 Minnesota DOT – ACEC Annual Consultant Conference
Pedestrian Treatments
Refuge Islands
2012 Minnesota DOT – ACEC Annual Consultant Conference
Installing pedestrian
refuge islands to
shorten the distance
and required
pedestrian clearance
time
2012 Minnesota DOT – ACEC Annual Consultant Conference
This permits the
required pedestrian
clearance time to be
reduced by
approximately 50%
depending on
crosswalk lengths
2012 Minnesota DOT – ACEC Annual Consultant Conference
New Technology
Queue Cutter Signal
2012 Minnesota DOT – ACEC Annual Consultant Conference
A Queue Cutter Signal is the most
cost effective tool available to
reduce advance preemption time
2012 Minnesota DOT – ACEC Annual Consultant Conference
A Queue Cutter Signal is a
separate traffic control signal
installed at a grade crossing
2012 Minnesota DOT – ACEC Annual Consultant Conference
A queue cutter signal is not connected to or
operated as a part of a downstream
signalized intersection
2012 Minnesota DOT – ACEC Annual Consultant Conference
Generally, a queue cutter signal is installed
where the Clear Storage Distance exceeds
400 - 450’
2012 Minnesota DOT – ACEC Annual Consultant Conference
Typical Queue Cutter Signal Layout
200 – 250’
Varies
Queue Loops
Queue loops must use fail-safe design and vital
loop processor system
Each loop wire has 2 independent loop circuits – a
detect loop and a check loop
Queue cutter signal flashes red if there is a loop
system failure
2012 Minnesota DOT – ACEC Annual Consultant Conference
Queue
Cutter
Signal
in
Los
Angeles
2012 Minnesota DOT – ACEC Annual Consultant Conference
Queue
Cutter
Signal
in
Los
Angeles
2012 Minnesota DOT – ACEC Annual Consultant Conference
2012 Minnesota DOT – ACEC Annual Consultant Conference
It is interconnected with the railroad
warning system with a small amount of
advance preemption time
This allows time for the queue cutter to
change to red before the railroad flashing
lights activate
2012 Minnesota DOT – ACEC Annual Consultant Conference
2012 Minnesota DOT – ACEC Annual Consultant Conference
2012 Minnesota DOT – ACEC Annual Consultant Conference
2012 Minnesota DOT – ACEC Annual Consultant Conference
When is a Queue Cutter not a
Queue Cutter?
When it’s a Pre-Signal
2012 Minnesota DOT – ACEC Annual Consultant Conference
Installed like a Queue Cutter
Looks like a Queue Cutter
Too close to the downstream
intersection to use queue
detection
2012 Minnesota DOT – ACEC Annual Consultant Conference
A Pre-Signal still requires full
Advanced Preemption Time from
the railroad
Why?
2012 Minnesota DOT – ACEC Annual Consultant Conference
Confusing to road users – is it a
pre-signal or near-side signal
faces?
Do I wait here or can I make a
right-turn-on-red?
2012 Minnesota DOT – ACEC Annual Consultant Conference
Pre-Signal
or
near side
signal
faces?
2012 Minnesota DOT – ACEC Annual Consultant Conference
CLOSING THOUGHTS
Remember – Preemption operation is not as easy as it
appears on the surface
Recognize – You need professional help to understand
and properly design the system
Understand - Connecting 2 independent systems
produces a third, more complex system
Grasp - The railroad is your friend – REALLY!
Plan - It will take longer and cost more than you think.
2012 Minnesota DOT – ACEC Annual Consultant Conference
Questions?
Rick Campbell
CTC, Inc.
[email protected]
817-886-8210