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TRB 2005, Session 628

Dave Holstein
Ohio Department of Transportation

PDF Version (400 kb)

Work Zone Impacts

  1. Capacity
  2. Safety/Crashes

There is a link between capacity and crashes.

  • 43% of all Ohio IR crashes occur on 12% of our IR system
  • Of this 12%, virtually all of it is over capacity
  • What does this have to do with work zones you ask?

Work Zone Impacts - Capacity

  • Thanks for asking
  • Work zones by their very nature reduce capacity
  • Exceeding capacity causes crashes
  • Work zone conditions can exasperate crashes (narrow lanes, clear zone issues, etc.)

Plan to Address WZ Capacity/Crashes

  1. Developed "Maintenance of Traffic Policy" to ensure satisfactory WZ capacity - 2000
  2. Developed MOT Alternative Analysis (MOTAA) to identify WZ "constraints" early in project development - 2003
  3. Developed process to monitor WZ crashes in near real-time - 2004

Plan to Address WZ Capacity/Crashes

  1. Maintenance of Traffic Policy = Proactive
  2. Maintenance of Traffic Alternative Analysis = Proactive
  3. Work Zone Crash Reporting = Reactive

The Policy Process

The chart shows how Ohio DOT implements their Maintenance of Traffic Policy on the Interstate. The process begins with the determination if the work zone will violate the permitted lane closure times. If the answer is 'no' the District Office may proceed with the design of the project and work zone traffic control plan. If the answer is 'yes' the Process checks for the anticipated traffic queue length and addresses those situations that require an exception to the Policy.

The ODOT MOT Policy

  • Established "Permitted Lane Closures (PLC)"
    • Hours each individual IR segment can have a lane reduction based on capacity
    • PLC times applicable to both maintenance and construction projects
  • Established maximum allowable queue impacts
  • Allowable queue thresholds
    • Queues less than 0.75 miles are acceptable
    • Queues greater than 0.75 miles and less than 1.5 miles if the queue exceeds 0.75 for two hours or less
    • 0.75 mile queues with a duration greater than 2 hours or longer than 1.5 miles are unacceptable
  • Established analysis process to determine queue impacts of projects that violate PLC
    • Utilize Quez98 program/ODOT spreadsheet/adjustment factors to predict queues
  • Established exception process that requires analysis of cost, schedule, queue impacts for numerous alternatives
    • Final decision is by executive committee (due to financial ramifications)

This figure is a screen capture of the Ohio DOT Permitted Lane Closure times for a specific portion of Interstate Highway. The permitted and not permitted lane closure times are shown in hourly increments for each day of the week with and with out construction.

  • Net results
    • Much more off peak hours and night time work (maintenance and resurfacing projects)
    • Spending $$$$$ to provide sufficient capacity in big projects
    • Systematic planning to provide sufficient work zone capacity

The MOT Alternatives Analysis

ODOT MOT Alternatives Analysis

  • What is it?
  • Analysis of potential work zone impacts "constraints" that occurs PRIOR to the first detail plan submissions
  • It occurs early enough so that MOT can be used to:
    • Pick between feasible project alternatives
    • Size structure widths
    • Highlight WZ right-of-way and environmental impacts early enough to do something about them

The figure shows the overall Ohio DOT Project Development Process for Major Projects. The Process includes fourteen steps beginning with defining the needs and goals of a proposed process and ending with the construction of the project. Work zone traffic impacts and control are first considered in step 6, Development of Alternatives. Exceptions to the Maintenance of Traffic Policy are addressed in step 7. The design of the project and the work zone traffic control plan is done in Step 8.


  • Designer is given a specific "desired" foot print (cross section) and then reports on a given list of potential problems
  • The number of lanes are based on the PLC
  • "Desired" foot print (cross section) is overlaid at defined location for both a crossover and part width alternatives.
  • Designer reports (for both crossovers and width) if any of the following problems would be expected:
    • Work zone policy
    • Maintain access (off-ramp capacity)
    • Ramp merges
    • Environmental impacts
    • Construction cost/duration
    • Maintenance of existing lighting/drainage
    • Construction joint location (concrete)
    • Crossover location
    • R/W impacts
    • Bridge widths
    • Earthwork, retaining walls, profiles
    • Constructability / Constr. Access
    • Provide "desirable" "footprint/cross section"
Factor to be consideredOption
Part-Width Construction (with partial demolition at bridges)
X-over Construction (without partial demolition at bridges
  1. OSE has indicated that partial demolition will provide acceptable factors of safety for a temporary condition. The cost for temporary demolition assumes that temporary piles and shoring of the existing bridge structures will not be required.
  2. Assume $1.0M base cost for MOT, plus additional MOT related items as identified in the chart above. This chart summarizes costs for the BUT-WAR-63 project, only.
Ability To Meet Work Zone PolicyFull closure of I-75 may be required at night, during partial demolition of the structure.Meets policy at all times.
Ability To Maintain All AccessesSimple access provided, utilizing two-step construction.Access to SR-63 will be provided using crossovers in Stage 3.
Ability To Provide On-Ramp Decision Sight DistancesMeets TEM requirements.Meets TEM requirements. See strip maps, Exhibits A through G.
Right-Of-Way And Environment ImpactsMOT scheme would not increase R/W or environmental impacts along I-75. Additional (minor) temporary easements are anticipated along SR-63, to facilitate placement of temporary pavement for part-width construction.MOT scheme would not increase R/W or environmental impacts along I-75. Additional (minor) temporary easements are anticipated along SR-63, to facilitate placement of temporary pavement for part-width construction.
Final Bridge WidthsMOT scheme does not impact proposed final bridge widths (approx. 78.5' face-to-face of barrier in both directions on I-75)MOT scheme does not impact proposed final bridge widths (approx. 78.5' face-to-face of barrier in both directions on I-75)
Significant Impacts For Construction Duration (See Note 2)Shortest construction duration on I-75. Bridges are constructed in two sequential steps, in the second construction season.Moderate. Construction of I-75 median area would occur in the first construction season (with minimal impact to existing traffic. I-75). Most construction would be completed in the second construction season (similar to Option 1). However, an additional one to three months would likely be required (in a third construction season) to complete median construction along I-75.
Significant Impacts To Permanent Earthwork, Retaining Walls, Etc.No impacts to these permanent design features are anticipated.No impacts to these permanent design features are anticipated.
Ability To Maintain Existing Drainage And Lighting SystemsNo special provisions required.Temporary drainage features and ditch work will be required in Stage 3 to maintain drainage in areas adjacent to x-over access to the SR-63 interchange ramps.
Constructability And Construction Equipment AccessAdequate and safe work zones along I-75. Potentially difficult contractor access is common with part-width construction.Improves contractor access and work space for construction of NB I-75. Facilitates efficient construction zones. Design of access to and from interchange ramps becomes more complicated, although is routine work for most contractors.
Ability To Meet TEM PolicyWould not meet minimum lane width requirements on the existing bridge decks. 33' face-to-face of barrier for three lanes would be provided (36' min. required per TEM), in second construction season.Conforms with lane width and shoulder widths required in the TEM.
Location Of Crossovers (e.g., can cross-over be located near the project?)The crossovers outside this project's limits will be constructed as part of BUT/WAR-75, designed by Balke.The crossovers outside this project's limits will be constructed as part of BUT/WAR-75, designed by Balke. The crossovers to maintain access to SR 63 can be provided with DSD in conformance with the TEM (see Strip Map Exhibits A through G).
Other Misc. MOT CostsTemporary pavement, embankment, and PCB on two sides of the freeway ($1.0M). Partial demolition required for three structures ($0.2M). (See Note 1.)Temporary pavement, embankment, and PCB on one side of the freeway ($0.5M). Temporary ramp crossovers are required to maintain access to SR 63 in Stage 3 (0.2M).
Estimated MOT Cost (See Note 2.)$2.2M$1.7M

This figure shows a plan view and multiple cross section views for a maintenance of traffic plan for a portion of Interstate highway.

ODOT MOT Alternatives Analysis

  • How/why did we develop this process?

    It started with our Director.

The ODOT MOTAA - How/Why

  • ODOT is embarking on the largest construction program(s) in our history
  • Director was concerned about the impact our work zones will have on crashes
  • Director's Question - Are the ODOT work zones causing more accidents?
    If so, can we do more to limit the increase?

The "Knee Jerk" Reaction

  • "Well of course we have more crashes in work zones. Narrow lanes, barriers next to lanes, and on... and on... . and on... ."
  • Turns out there were things we could do better!!

The Analysis

  • Began analyzing work zone crashes
  • Performed "Before/After" comparison of crash rates
  • Results were startling:

This computer screen capture shows the crash rates for a portion of Interstate highway with and without a work zone. In this example the work zone crash rate is approximately double the free flow situation. In this case and investigation of the cause and possible solutions would be under taken.

This is another example of crash rates with and with out a work zone. Again, the work zone rate is higher than the free flow condition. Ohio DOT's goal is to not exceed the free flow crash rate in their work zones.

Next Step -> More Analysis -> The Conclusions


The "abnormally" high concentrations of crashes showed there are major geometric contributing factors to work zone crashes:

  1. Inadequate off-ramp capacity (not covered by MOT policy)
  2. Inadequate ramp merges
  3. Insufficient paved shoulders

The Geometric Problems

  • Ramp merges - Created new standards for work zone on ramp merges. Merges are now required to be detailed in plans. (Problems noted in MOTAA)
  • Paved shoulders - Created "desired" cross section that requires a 2' paved shoulder (Problems noted in MOTAA)
  • Off ramp capacity - Explicitly looked for in Maintenance of Traffic Alternative Analysis (MOTAA).


  • So what does all this have to do with the MOTAA?
  • The MOTAA is also a process that ensures we won't replicate the geometric problems discovered through our crash analysis

Net Result:

  • Past problems don't get replicated
  • Potential WZ problems are identified early in the project development process when there is still time to take action
  • Identifies "best" option for a WZ (part width, crossover, contra flow, hybrid)
  • Problem "fixes" are scoped into the subsequent detail design steps of the process
  • Identifies important innovative contracting opportunities

Work Zone Crashes

Work Zone Crashes - Reactive Measures

  • ODOT is obtaining work zone crash reports in nearly real time from local law enforcement.
  • Crashes are input into a database application that sorts crashes into one half-mile segments for comparison to historical pre-construction average crash frequency.

This bar graph plots several sections of an Interstate highway. For some sections of highway the work zone crash rate is below the average free flow crash rates and in other sections the work zone crash rate is higher. These graphs are used by Ohio DOT traffic engineers and managers to evaluate the effectiveness of the work zone traffic control plans over several sections of highway and for multiple years.

  • Work zone crash reports are used to look for "abnormally" high concentrations of crashes.
  • When found field visit ensues to find causes and fixes.

Misc. MOT Topics

Related MOT Topics

  • Every Interstate and look-alike work zone is inspected and rated by Central Office for adherence to standards, specifications and for safety concerns
    • Any safety concerns are immediately brought to the attention of the district for correction
    • Results of these inspections are part of Organization Performance Index (OPI)
    • Each District Deputy Director is held accountable for their OPI performance
  • ODOT undertaking largest training initiative in our history
    • One of the many required classes (for 2500 ODOT highway workers, project inspectors, etc) is work zones
    • Testing and certification are part of the training classes
  • Consultants now required to attend ODOT WZ Design training class as part of their prequalifications. Testing & certification required.
Misc. MOT Topics
  • More open to complete closures; particularly for urban bridge overlays.
  • Maximum deck area is currently 23,000 square feet
    • Close Friday @ 8 pm
    • Open for Monday rush hour
    • Must be cautious of "blow throughs"
  • Ground Penetrating Radar

This figure shows a plan view of a bridge deck and the identification of delaminated areas of the deck. This information is used in designing the rehabilitation strategy for the deck. The specific correction action dictates the type and duration of traffic control need to accomplish the work.


More Information



Scott Wolf
Center for Accelerating Innovation

PDF files can be viewed with the Acrobat® Reader®
Updated: 04/04/2011

United States Department of Transportation - Federal Highway Administration