Bureau of Transportation Statistics (BTS)
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Figure 1 Estimating Average Effective Speed

Figure 1 Estimating Average Effective Speed. If you are a user with disability and cannot view this image, please call 800-853-1351 or email answers@bts.gov for assistance.

Key:
VCURVE = the maximum allowable speed on a curve
VROUGH = the maximum allowable ride-severity speed
VSPLIM = the maximum speed resulting from the speed limit
FFS = free flow speed
FFSUP = free-flow speed on an uphill
D = delay
AES = average effective speed