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The greatest use of Traffic Trends is for expanding a short duration count into an AADT by applying the factors contained in the following tables. The longer the actual count duration, the more accurate the final result. Through the use of factors for the individual stations, short term counts can be expanded to estimated AADT's, and various traffic characteristics can be imputed, for the count locations.
Examples:
- Assume a 12 hour count (7AM-7PM) of 10,000 vehicles from a Wednesday in March on a highway on which traffic is considered to similar to the characteristics of Group 2 - Rural Other:
Step 1 - Obtain the factor (1.33) for a March Wednesday in the "7AM-7PM" table on Page GF5 Rural Other. Multiply the 12 hour count of 10,000 by 1.33 to get a 24 hour total of 13,300.
10,000 x 1.33 = 13,300
- Assume a 48 hour count at a location on MD 17 where you believe traffic is similar in characteristics, but not in volume, to ATR #03 taken on a Tuesday and Wednesday in June.
Assume the count on Tuesday was 3,500 and on Wednesday, the count was 3,600.
Step 1 - Use the factor (0.96) from June Tuesday in the "24HR" table on Page 12. Multiply the Tuesday total by 0.96.
Step 2 - Use the factor (0.94) from June Wednesday in the "24HR" to AADT table on the same page. Multiply the Wednesday total by 0.94.
Step 3 - Add the results from Step 1 and Step 2 and divide by 2.
| Step 1: 3,500 x 0.96 = |
3,360 |
| Step 2: 3,600 x 0.94 = |
3,384 |
| 6,744 |
| Step 3: divide by |
2 |
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| AADT |
3,372 |
Note: Axle Correction Factors must be applied to volume counts (such as counts taken with a single road tube sensor) that do not directly convert the number of axle pulses into vehicle counts like classification counts. Axle correction factors are calculated by functional classification utilizing all vehicle classification counts taken during the calendar year.
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