Highway Safety Manual applied in Missouri - freeway/software : research summary.
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Highway Safety Manual applied in Missouri - freeway/software : research summary.

Filetype[PDF-663.62 KB]

  • English

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    • Abstract:
      AASHTO’s Highway Safety Manual (HSM)

      includes models for freeway segments, speedchange

      lanes (transitional area between mainline

      and ramps), ramps, and interchange terminals.

      These predictive models for freeway

      interchanges need to be calibrated to Missouri

      conditions. This calibration process requires

      detailed data types, such as crash frequencies,

      traffic volumes, geometrics, traffic control, and

      land-use. The calibration process also requires

      specific decisions on the correct sampling

      approach, determination of the influence area of

      terminals and interchanges, and how to locate

      crashes within the appropriate interchange


      In order to obtain samples for each interchange

      facility type, every single freeway interchange

      in Missouri was catalogued according to HSM

      classification. This was done since the

      Transportation Management System (TMS)

      database does not classify interchanges

      according to the HSM definitions. Freeways in

      Missouri include interstates, US highways, and

      Missouri highways. From this master list of all

      Missouri interchanges, sample sites were selected randomly while maintaining

      geographical coverage across all seven MoDOT


      HSM calibration is a data-intensive process that

      uses many types of data. One type is geometric

      data which involves the collection of

      characteristics such as lane width, shoulder type,

      median type, ramp skewness, horizontal

      curvature, and traffic control. Another type is

      AADT which is obtained by querying the

      MoDOT TMS database. A third data types is

      crash data which requires the detailed review of

      original crash reports, since crashes were

      frequently landed incorrectly.

      The project calibrated various Missouri freeway

      interchange facilities, including diamond, partial

      cloverleaf, and full cloverleaf interchange

      terminals, and ramps and speed-change lanes.

      Missouri interchanges can now be modeled

      using these calibration values with the HSM.

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