Design Hourly Volume from AADT

DHV = AADT \times K \times D

AADT is the two-way average annual daily traffic. K is the design-hour factor (proportion of AADT in the 30th-highest hour, often 0.08–0.12). D is the directional distribution in that hour (often 0.55–0.70). DHV is one-way design-hour volume used to size the facility. ADT without the annual average is a shorter-count estimate.

$AADT$ (veh/day): Average annual daily traffic (two-way)
$K$: Design-hour factor
$D$: Directional distribution factor
$DHV$ (veh/h): Design hourly volume (one-way)

Step-by-step solved example

AADT = 25,000 veh/day, K = 0.12, D = 0.60. Find DHV.

AADT scaled by K and D to a directional design-hour volume.

1. Two-way design hour
K × AADT = 0.12×25000 = 3000 veh/h (both directions).
$K \times AADT = 3000$
2. One-way DHV
DHV = 3000×0.60 = 1800 veh/h.
$DHV = 1800 veh/h$

Answer: 1800 veh/h

10 practice questions

0/10 correct

1.AADT = 10,000, K = 0.10, D = 0.55. DHV =

2.K-factor is typically

3.If D = 0.50, traffic in the design hour is

4.AADT itself is

5.Rural recreational routes often have K

6.Two-way design-hour volume is AADT × K. With AADT = 40,000 and K = 0.09 that is

7.Lane distribution further splits DHV among lanes. The shoulder lane often carries

8.D cannot be less than

9.AADT = 8,000, K = 0.15, D = 0.70. DHV =

10.Using ADT from a 48-hour count instead of AADT introduces