35 Work Zones
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Transcript 35 Work Zones
Work Zone Traffic Control
CE 453 Lecture 35
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Objectives
Describe a maintenance of traffic plan for
a roadway project
Define work zone problems and reasons
for same
Identify work zone traffic control devices
Present details of work zone traffic control
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Key resources …
http://mutcd.fhwa.dot.gov/ - contains
standards and principles for design,
installation, and maintenance of traffic
control devices in work zones
http://wzsafety.tamu.edu/
AASHTO Roadside Design Guide: Chapter 9 discusses:
Traffic Barriers, Traffic Control Devices and Other
Features in Work Zones. Should be used with Traffic
Control Devices Handbook – Part VI
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http://safety.fhwa.dot.gov/fourthlevel/pdf/bestprac.pdf
Maintenance of Traffic Plans
How/when traffic is maintained during
construction
Typically required/not always – really needed
Include the following (if needed):
Diversion/detour alignments
Tapers and lane drops (see MUTCD)
Pedestrian accommodations
Traffic control (signals, sign type, sign location)
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http://www.fhwa.dot.gov/tfhrc/safety/pubs/89035/89035.pdf
Maintenance of Traffic Plans
Pavement marking, cones, barriers for
channelization
Illumination and warning lights (steady for
path, flashing for single points)
Policies for removal of signs, etc.
Staging of Traffic (how it flows)
Need for flaggers, etc.
Notes (e.g, move or sign all equipment when
not in operation in the work zone)
No parking of employee cars in work zone
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Maintenance of Traffic Plans
Cost estimate must include labor, signs,
cones, etc.
Often not given proper time or attention –
switching time most dangerous
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Why are Work Zones more Prone to
Crashes?
Why are work zones difficult for drivers
and subsequently dangerous for workers?
Violate – Expectancy
Increased – Workload
Combine – Both
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Work Zone Safety Facts
Late 90s … ~700 deaths/year … now, ~1000!
Tractor/trailer involvement in work zones
crashes are high (26% of fatalities)
Work Zone crashes generally more severe
(more injuries/fatalities than national average)Fixed object impacts result in more
injuries/fatalities than vehicle to vehicle impacts
½ of work zone fixed object impacts occur at
night (impact on staging??)
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Work Zone Safety Facts
1994-98 Average was that 16% of work
zone fatalities were peds/bicyclists
Fatal work zone crashes are twice as
high as non-work zone fatals on urban
interstates (14% are FATAL!)
The majority of fatal work zone crashes
occur on 55 mph or greater speed limits
(No need for slow speed MOT?
Ped/bike/ car fatalities? – increase over
35 mph but occur much lower)
29% of fatals on weekends! (most in
summer and fall)
~150 workers killed each year (who are
the workers???)
Utility work in bike lanes can
often be accomplished without
blocking the entire lane.
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http://safety.fhwa.dot.gov/ped_bike/univcourse/swless12.htm
Number of Work Zone Fatalities - 2002
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http://www.dot.state.ia.us/workzone/index.htm
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Work Zone Traffic Control Devices
Cones/Tubular Markers
Vertical Panels
Drums (watch breakaway lamps –
ballast at bottom and no greater than
25 kg)
Barricades Type I, II, and III
Shadow Trucks, etc. for moving
construction or maintenance
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Work Zone Traffic Control Devices
Temporary barriers (Portable Concrete Barrier (PCB)
used by many states - uses: bridge widening,
shielding roadside structures, roadway widening, and
the separation of two-way traffic on a normally
divided roadway)
Glare Screens (block view of construction, for design
consider separation distance, vertical curvature,
horizontal curvature)
Signs and Supports – meet normal specifications –
breakaway within clear zone, etc. (MUTCD)
Warning lights (minimum height 3 ft. or 900 mm –
securely fasten and battery on ground – why?)
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Detour considerations
Speed
Capacity
Distance
Safety
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How to increase detour
capacity
(e.g., during I-235 reconstructions – Univ. Ave., etc.)
eliminate some turns
reroute some trucks and buses
ban parking
ban loading/unloading during peak
eliminate some bus stops
coordinate signals
widen the traffic way
implement one-way
ITS??? (incident management, esp.)
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http://www.dot.state.ia.us/design/e00_toc.htm#Chapter_9
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Specifics for Work Zones
Fundamental principles of work zone
traffic control design
Four work zone areas and their
components
Taper lengths and types
Advance signing applications and
factors that impact setup
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Work Zone Traffic Control Design –
10 Fundamental Principles (MUTCD Part 6)
Why? worker/motor vehicle safety in temporary
traffic control areas
Traffic safety must be integral and high-priority
during project development (from planning to
construction) and rehab/ maintenance or utility
activities
Follow same principles of normal permanent
roadside/roadway designs (goal is use
comparable geometrics/traffic control if
possible)
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Fundamental Principles (cont.)
Produce a traffic control plan (TCP)
(understand before field work)
Traffic should be inhibited as little as practicable
Avoid frequent and abrupt geometry changes
Provide for incident management vehicles
Minimize work time and do off-peak if possible
Guide drivers/peds in a clear and positive
manner approaching and through zone
(adequate traffic control, proper action with
permanent control, flagging)
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Fundamental Principles (cont.)
Routinely inspect your traffic control elements
Maintain the roadside during construction (for
safety)
Train all levels of workers in temporary traffic
control zone safety
Provide statutes that allow work zone traffic
control (no real engineer control???)
Maintain good public relations (media)
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Activity Area
Storage
(not shown)
Work
Buffer
Traffic
4. Termination
Area – returns
traffic to normal
3. Activity Area –
where the work
happens
2. Transition
Area – channels
the traffic
1. Advance Warning
- what to expect
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Older AASHTO
New MUTCD
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Tapers – Important Safety Element of
Work Zones (Why?)
Used in transition and possibly termination
areas of work zone
Use a series of channelizing devices and/or
pavement markings
Observe after implementation (adjust as
appropriate)
Channelizing device spacing (in feet)
approximately equal to the roadway speed in
MPH
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Taper Lengths (See Table next page)
40 mph or less L = WS2/60
45 mph or greater L = WS
L = taper length in feet
W = width of offset in feet
S = Posted speed, off-peak 85th percentile
speed before work, or anticipated
operating speed in MPH
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Taper Types
Merging – longest because it requires drivers to merge
with other traffic (use L minimum)
Shifting – merging not required, but a lateral shift is (use
½ L minimum)
Shoulder – used where shoulder may be mistaken for
driving lane (use 1/3 minimum, but L is traveled on)
Downstream – provide visual cue that original lane is
now accessible (optional – if used 100 feet/lane
minimum, 20-foot device spacing)
One-lane, Two-way – used when one lane closed and
used by both directions (use 100-foot maximum and typ.
flagger)
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Warning Signing for Typical Applications
Place warning signs in advance of work areas
at spacing indicated
Distances measured from transition or point of
restriction start
Table 6C-1 suggests spacing for warning signs
on different roadway types
• “A” is distance from transition/point of restriction to first
sign
• “B” is distance to from first to second sign, and
• “C” is distance from second sign to initial sign
encountered by driver (in a three-sign series)
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Selecting a Typical Sign Setup
Consider:
Duration of Work (long-term stationary,
intermediate-term stationary, short-term
stationary, short duration, and mobile)
Location of Work (e.g., outside shoulder,
near/on shoulder, median, on roadway)
Roadway Type (e.g., rural two-lane, urban
arterials, other urban arterials, rural or urban
divided/undivided, intersections, and freeways)
• MUTCD has 44 typical applications split by these
categories
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I65 Work Zone, North of Louisville
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