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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 devicesPresent details of work zone traffic control

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http://safety.fhwa.dot.gov/fourthlevel/pdf/bestprac.pdf

http://wzsafety.tamu.edu/

Key resources …

http://mutcd.fhwa.dot.gov/ - contains standards and principles for design, installation, and maintenance of traffic control devices in work zones

AASHTO AASHTO Roadside Design Guide:Roadside Design Guide: Chapter 9 Chapter 9 discusses: Traffic Barriers, Traffic Control Devices discusses: Traffic Barriers, Traffic Control Devices and Other Features in Work Zones. Should be and Other Features in Work Zones. Should be used with Traffic Control Devices Handbookused with Traffic Control Devices Handbook – Part – Part VVII

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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)

http://www.fhwa.dot.gov/tfhrc/safety/pubs/89035/89035.pdf

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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???)

http://safety.fhwa.dot.gov/ped_bike/univcourse/swless12.htm

Utility work in bike lanes can often be accomplished without blocking the entire lane.

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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

SpeedCapacityDistanceSafety

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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 typesAdvance 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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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)

Fundamental Principles (cont.)

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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)

Fundamental Principles (cont.)

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1. Advance Warning - what to expect

2. Transition Area – channels the traffic

3. Activity Area – where the work happens

4. Termination Area – returns traffic to normal

Traffic

Buffer

Work

Storage(not shown)

Activity Area

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New MUTCD

Older AASHTO

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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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