85th percentile speed of private
cars (mph)
x-height (mm)
Triangle height / roundel
diameter (mm)
Up to 20
60
450
21 to 30
80
600
31 to 40
100
750
41 to 50
120
900
51 to 60
160
1200
61 to 70
200
1500
70 mph speed limit
240 (300)
1800 (2250)
NOTES
1. The height or diameter of the triangular or circular roundel shown above is based upon 30 stroke
widths, the most common size. For S12‑20‑25 or 27 (structural weight limit or prohibition of vehicles
carrying dangerous goods), this reduces to 24 sw.
2. 85th percentile speed measurement is dealt with in TA 22 ‘Vehicle speed measurement on all‑purpose
roads’ in Volume 5 of DMRB (see
1.5.1
). The “dry weather spot speed” should be used. This is the speed
only exceeded by only 15% of the cars.
88
Chia sẻ với bạn bè của bạn: |
