work zone traffic control

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Work Zone Traffic Control

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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

3http://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. Direct link to pdf version: http://mutcd.fhwa.dot.gov/pdfs/2003r1/pdf-index.htm

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 (MOT) or Traffic Control Plans (TCP)

• A plan directed to the safe and expeditious movement of traffic through construction and to the safety of the work force performing those operations

• How/when traffic is maintained during construction

• Typically required … always needed• Often not given proper time or attention –

switching time most dangerous

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

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• 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 • Cost estimate must include labor, signs, cones, etc. • Include the following (if needed):

– Diversion/detour alignments– Tapers and lane drops (see MUTCD)– Pedestrian accommodations– Traffic control (signals, sign type, sign location)

Plan Components

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This page includes links to databases and web sites of standards, specifications, and practices that are related to work zone safety.

  Work Zone Safety Standards and Practices Database   Manual on Uniform Traffic Control Devices (MUTCD)   Visibility and Retroreflectivity Related   OSHA Regulations   Best Practices on Work Zone Safety   FHWA's National Highway Specifications   FHWA's Work Zone Mobility and Safety Fact Sheets   Work Zone Traffic Control Inspection Forms

http://wzsafety.tamu.edu/files/S&P.stm

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Special conditions in TCP

• High volume or high speed traffic.• Rush hour or seasonal traffic patterns.• Heavy use by pedestrians.• Changing work conditions or other conditions

that would be confusing to the traveling public.• Hazards due to nighttime operations.• Complex detours or traffic patterns.• Closely spaced intersections, interchanges, or

other decision points.

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Checklist of factors

• Estimated traffic volumes, vehicle types, and direction of travel.• Traffic speeds.• Required number of travel lanes.• Traffic control layouts including signing, markings, channelization

devices, traffic signals, traffic• delineators, barriers, and detour schemes.• Restrictions on work periods such as rush hours, holidays, special

events, nights, weekends.• Characteristics of adjacent highway segments.• Requirements for partial completion and opening sections to traffic.• Maneuvering space available for traffic.• Requirements for installing, maintaining, moving, or removing traffic

control devices.• Turns or cross movements required by traffic.

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Additional Considerations(but not in contract)

• The need for public relations, such as notifications to the local news media.

• Any special agreements reached with other agencies relating to traffic control or traffic management.

• Accident reporting requirements.• Any special guidance on traffic management for the

project engineer.

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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 … 1074 in 2005!• 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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Temp. Traffic Control Devices & Signs

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http://tti.tamu.edu/documents/0-4692-1.pdfTTI study of portable concrete barrier design

Temporary barriers - Portable Concrete Barrier (PCB)

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40Transpo Industries web site

617.1.5 Temporary Glare Screens. Temporary glare screens in work zones consist of modular units installed on top of temporary concrete traffic barrier. Temporary glare screens prevent headlight glare. Glare screens may also be used to block the driver’s view of construction activities. Glare screens are not used where they could restrict driver visibility and sight distance. Use of these units are limited due to installation and maintenance concerns to areas where work zone activities could impact the flow of traffic, or geometrics could create a blinding effect on drivers. When specified, quantities are calculated and shown on the plans. - MODOT

Glare screen should not be installed in medians wider than 6.1 m. -CalTrans

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BMW Takes On Glare Screen

WSDOT's IRT member Don Harris said the weekend accident on westbound SR 520 near 92nd Avenue was one of the more unusual situations to which he’d responded.  The driver of a BMW lost control and drove for 780 feet on the jersey barrier, taking out 640 feet of glare screens.  The screens are on top of the jersey barrier to prevent the headlights of opposing traffic from blinding or distracting drivers. Harris’s job was to pick up all those glare screens while WSP Troopers took custody of the driver. Traffic was up and running again shortly after the 8:15 a.m. accident.

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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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• 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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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 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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When conditions are more complex, use …

A. Additional devices:1. Signs2. Arrow panels3. More channelizing devices at closer spacing

(see Section 6F.68 for information regarding detectable

edging for pedestrians)4. Temporary raised pavement markers5. High-level warning devices6. Portable changeable message signs7. Temporary traffic control signals (including

pedestrian signals and accessible pedestrian signals).

8. Temporary traffic barriers9. Crash cushions10. Screens11. Rumble strips12. More delineation

B. Upgrading of devices:1. A full complement of standard pavement

markings2. Brighter and/or wider pavement markings3. Larger and/or brighter signs4. Channelizing devices with greater conspicuity5. Temporary traffic barriers in place of

channelizing devices

C. Improved geometrics at detours or crossovers

D. Increased distances:1. Longer advance warning area2. Longer tapers

E. Lighting:1. Temporary roadway lighting2. Steady-burn lights used with channelizing

devices3. Flashing lights for isolated hazards4. Illuminated signs5. Floodlights

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Research comparisons on Control Devices

• Cones, signs and barricades more effective in conjunction with a flagger

• Barricades, panels, and drums lead to earlier transition time at night than did cones and tubes

• Size and visible area of control device had more impact than shape

• Only arrows and chevrons successfully conveyed the message of direction (not stripes)

• Generally, devices of equal visibility had equal value• Motorists respond to the channelization path, but not to a

single device

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OECD Research comparisons on devices

Cones and tubes advantages• provide less impediment to traffic flow• Cause less damage to vehicles and workers• Easier to store, transport and set up?• Smaller “projectile” than drums• Don’t blow over as easily

Disadvantages• easy to penetrate/displace• don’t command respect as drums

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http://www.aaafoundation.org/pdf/PEDO_report.pdf

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Edge drops in Construction Zones

http://www.ctre.iastate.edu/reports/dropoff.pdf

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Edge drop mitigation in construction zones

• Place a 45 degree wedge at drop-off site– What are the potential problems?

• Place channelizing devices near drop-off using a 3 foot buffer

• Install portable concrete barriers (or other barrier type)

• What factors affect the wisdom of doing this?

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