Traffic Violations Indicator (TVI) Methodology

Using (1) traffic violation (TV) data collected in conjunction with Level 1, 2, and 3 roadside inspections within the last 24 months and (2) the average number of power units from the Motor Carrier Census, SafeStat calculates the TVI for each carrier with a minimum of three TVs from three different inspections. SafeStat assigns a weight to each TV by its age and whether it is a specified TV, (see table below), or an unspecified TV, i.e., 392.2 (General/Local Law). The sum of the weighted TVs is normalized by the number of average power units to obtain the Traffic Violations Measure (TVM). Carriers with similar numbers of power units are grouped, compared to one another by their TVMs, and ranked by percentile within each group. SafeStat assigns a percentile number to each carrier’s TVI, based on that rank.

Traffic Violation Data

In calculating the TVI, SafeStat uses traffic violations recorded in conjunction with Level 1, 2, and 3 roadside inspections over the last 24 months. There is a minimum number of three inspections with TVs for SafeStat to consider the data sufficient to calculate a TVI for a carrier.

SafeStat uses the following data elements from roadside inspections in its calculations of the TVI:

• Number and type (i.e., specified or unspecified) of Traffic Violations
• Date of Traffic Violation

Specified Traffic Violations are identified as follows:

Unspecified Traffic Violations are identified as 392.2 (General/Local Law)

Census Driver Data

SafeStat computes the TVI using the number of traffic violations normalized by the average number of power units contained in the Census data. The primary sources of power unit information in the Census are Forms MCS-150 and MCS-151. When the Census data on the average number of power units for a carrier are suspect, specific state/federal organizations are contacted to obtain the most accurate value.

Calculation of the Traffic Violations Measure (TVM)

SafeStat calculates the TVM by adding the weighted number of traffic violations and dividing by the average number of power units. The equation for the TVM is:

SafeStat time weights violation data by assigning a value of 1,2, or 3 to each violation data to give more relevance to recent violations. The following steps detail SafeStat’s calculation of the TVM.

1. Using the traffic violations (TV) listed in roadside inspection data, aggregate each carrier’s inspections with TVs into three periods based on the age of each violation: 0 to 6 months, 7 to 18 months, and 19 to 24 months into one of two groups, (1) inspections with specified violations (as noted in the above table) and (2) inspections with no specified violations but with 392.2 (General/Local Law) violations. For inspections in Group (1), the number of specified TVs is counted. Inspections with neither specified nor unspecified TVs are disregarded in the calculation of the TVM.

   

   *Multiple counts of the same specified TV are counted only once (example: one inspection with three 392.4A violations will be counted only once)

2. Multiply the appropriate time weight (3 for 0 to 6 months, 2 for 7 to 18 months, 1 for 19 to 24 months, or half these values for the 392.2 General/Local laws) by the number of specified TVs in each of the three time periods and sum all three groups to obtain the time-weighted number of specified TVs. Apply the time weight to the number of inspections with only unspecified TVs and then multiple the sum by 0.5 to give the unspecified TVs half the weight of the specified TVs.

   

3. The Unspecified TVs are given half the weight of the Specified TVs. To obtain the Total Weighted TVs, add the Time-Weighted Specified TVs to one-half the Time-Weighted Unspecified TVs.

   

4. Calculate the average number of PUs over 24-month time frame by determining the number of PUs at the end of each of the three time periods.

   

5. Divide the Total Weighted TVs by the average number of power units (PUs) to obtain the TVM.

   

Calculation of the Traffic Violations Indicator (TVI)

SafeStat uses the TVM to calculate the TVI. The following steps detail SafeStat’s calculation of TVI.

1. Remove all carriers with fewer than three inspections with any TVs. For the remaining carriers, determine the total number of power units for each carrier, and place each carrier into one of four groups shown below:

   

2. Within each group, rank all the carriers’ TVM values in ascending order. Transform the ranked values into percentiles from 0 percentile (representing the lowest TVM) to 100th percentile (representing the highest TVM). Assign the percentile value to the TVI.

Calculation of the Driver SEA Value

The Driver SEA Value establishes the carrier’s safety status concerning driver operations. SafeStat uses the Driver Inspections Indicator (DII) and the Driver Review Indicator (DRI) and the Traffic Violations Indicator (TVI) with their associated indicator weights to calculate the Driver SEA Value.<>

The Driver SEA Value calculation is the maximum of the DRI, DII, and TVI.

If none of the indicators exist (DRI, DII, or TVI) then the carrier has insufficient data for SafeStat to calculate a Driver SEA Value.