Permitted Lane Closure

FAQ & Definitions

FAQ

1. Why are the permitted lane closure (PLC) times occasionally referred to as maps?
   Initially, districts submitted maps showing roadway sections which could not be closed during particular hours.  In the future, interactive online maps may be added for each county to show which routes are subject to the Permitted Lane Closure policy.  ODOT’s Traffic Engineering Manual refers to the system as the Permitted Lane Closure Schedule.
2. How are the statewide hourly percentages calculated?
   The statewide percentages are composite percentages from ATRs on the interstate and freeway systems.  These are updated annually and can be found at:
   
   https://www.transportation.ohio.gov/programs/technical-services/traffic-monitoring/hourly-percent-by-vehicle
3. What are the differences between the calculation methods A, B, C, and D?
   The District Work Zone Traffic Managers have several traffic volume count methods they can choose from to determine how lane closure times can be calculated.
   
   The calculation methods and differences, ranked in order of priority are:
   
   

   • Method A – ATR – actual hourly volumes for section: the ATR is located within the section
   • Method B – ATR – hourly percentages applied to factored AADT: the ATR is upstream or downstream of the section on the same route
   • Method C – ATR – hourly percentages from a close ATR applied to factored AADT: the ATR is on a different route or in a different county
   • Method D – AADT – hourly percentages from statewide distribution applied to factored AADT
4. How often are traffic counts taken?
   Traffic counts are usually collected every three (3) years.  A roadway could potentially have three (3) or four (4) years with the same permitted lane closure times. At times a count may have been taken but not yet published before the annual update to the PLC map/schedule occurs.
5. How does this compare with the PLC times using an ATR?
   The ATRs are constantly recording traffic data.  When using ATR data, the permitted lane closure times should be closer to the actual current field conditions. However, if any data is missing from an ATR recording during February, May or August of the year in question the PLC map/schedule system will either default to the prior year of recording data or the segment need to be directed to utilize a different calculation method (B, C or D) in the case of no complete ATR data within the prior two years from time of calculation.
6. Are truck percentages calculated from the ATRs by season, by day, or by year?
   All truck percentages will be by year using the average from the roadway inventory.  This percentage will be used from ATR or AADT calculation methods.
7. Why do the closures differ on the multiple-section chart compared to the single-section chart?
   The multiple-section chart summarizes information for all sections within a district, county, or route.
   
   The single-section chart shows all information on a single section, including hourly traffic volumes.
   
   The multi-section chart makes an assumption for allowable work hours.  If the section has one (1) hour where the lane is permitted to be closed between hours where it is not permitted, the program will not count the available hour.  If the section has two (2) hours available, the program will count the available hours.
8. Where did the reference to holiday work come from?
   The note for this work comes from Section TEM 642-6 of ODOT’s Traffic Engineering Manual.  The District Work Zone Traffic Manager can include more holidays or specify special events at their discretion. The TEM can be located here: https://www.transportation.ohio.gov/working/engineering/roadway/manuals-standards/tem

Definitions

• ATR – Automatic Traffic Recorder – This is a device which is able to count and classify vehicles for each day of the year.  The device consists of loop detectors and a microprocessor controller with modem.  The ATRs used for PLC must have bi-directional counts for Thursdays, Fridays, and Saturdays for the months of February, May, and August from the 1st through the 20th.
• AADT – Annual Average Daily Traffic – the average 24-hour traffic volumes at a given location for a full year.  AADT is a bi-directional volume.
• Truck Percentage – the percentage of Class B and C vehicles (semi-trailers) within a given section
• Seasonal Adjustment Factors – factors used to adjust the AADT to the winter, spring/fall, and summer season for the calculations.  The factors are calculated from ATRs and can be found at: 
  https://www.transportation.ohio.gov/programs/technical-services/traffic-monitoring/seasonal-adjustment-factors
• Winter season – December 1 - February 29
• Spring/Fall season – March 1 – May 31 and September 1 – November 30
• Summer Season – June 1 – August 31
• Road Class – A segment can be classified as rural or urban.  This classification affects each segment’s hourly distribution and determines which days are used to calculate the weekday and weekend.
• Terrain Type – A segment can be labeled as having level or rolling terrain.  This affects the capacity of the lanes due to the effect of grades on trucks.  Rolling terrains have less capacity than level terrains.
• Weekday Closures – Weekday closures for RURAL segments are defined as closures occurring Monday-Thursday.  Weekday closures for URBAN segments are defined as closures occurring Monday-Friday.
• Weekend Closures – Weekend closures for RURAL segments are defined as closures occurring Friday-Sunday.  Weekend closures for URBAN segments are defined as closures occurring Saturday-Sunday.
• Number of Lanes Available per Direction – This number reflects the number of through lanes for that direction.
• AADT Year/ATR Year – This is the year that the AADT/ATR volumes were taken.
• Work Zone Lane Capacity – This is the theoretical lane capacity for each lane within the section. The Highway Capacity Manual 2010, Equation 10-9 was used to determine theoretical capacity of the roadway lane. The calculation has been simplified to only use two variables: terrain and truck percentage.