Quiet Zone Risk Index (QZRI)

A QZRI must be calculated whenever SSMs are not installed at all crossings. To calculate a QZRI, the following procedure is followed:
  • Determine crossing Risk Index with Horns (RIWH) for each public at-grade crossing in
    proposed
     Quiet Zone prior to any adjustments for SSM effectiveness.
  • Determine Crossing Risk Index (Crossing Risk Index = RIWH * 1.668 * (1-Effectiveness)) for each public at-grade crossing in
    proposed
     Quiet Zone after any current or planned SSMs/ASMs are installed.
  • Determine RIWH (average of crossing RIWH in absence of any existing or proposed SSMs for all public at-grade crossings in Quiet Zone).
  • Determine QZRI (average of Crossing Risk Index for all public at-grade crossings in Quiet Zone).
The initial RIWH calculation may be determined from the FRA website Quiet Zone Calculator and is a calculation based on:
  • AADT.
  • Trains per day.
  • Number of day through trains.
  • Total switching trains per day.
  • Number of main tracks.
  • Number of other tracks.
  • Crossing
    location
     (urban or rural location).
  • Roadway
    surface
     (paved or
    unpaved
    ).
  • Maximum train speed.
  • Number of roadway lanes.
  • Number of years of crash data.
  • Number of crashes in crash data years.
Note that
 any existing grade separated or closed crossings may not be considered when calculating the QZRI. For any proposed closed crossings, the existing traffic counts at the crossing must be distributed among adjacent crossings for AADT calculations.