APPENDIX F

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VICROADS INFORMATION ON VEHICLE SPEED EFFECTS

Preliminary 'before' and 'after' speed zone data measured along 4 roads within each speed zone category affected by the revision of speed limits revealed that for:

(a) Undivided Roads Changed from 60 km/h to 70 km/h

• There was a general increase in vehicle speeds in the order of about 3 km/h.

• The proportion of motorists exceeding the posted limit fell sharply, while the high risk drivers, travelling at greater than 20 km/h over the posted limit also dropped dramatically.

• Vehicle speeds remained relatively unchanged.

• The proportion of motorists exceeding the posted limit fell markedly.

• The at risk motorists 'speeding' (ie. travelling at greater than 20 km/h above the posted limit) decreased dramatically.

• The speed distribution, or spread of speeds of the driving population reduced. Studies have shown that this characteristic provides positive safety benefits.

• Vehicle speeds decreased only slightly, in the order of about 3 km/h, while at 3 of the 8 locations measured, motorists drove excessively over the posted limit (more than 20 km/h).

• With the exception of one location (of 8) the proportion of motorists exceeding the posted limit increased.

• Vehicle speeds were relatively unchanged.

• The proportion of motorists travelling below the posted limit dropped sharply.

• The proportion of 'speeding', or high risk (travelling at more than 20 km/h above the posted limit) motorists remained unchanged.

(e) Undivided Roads Changed from 75 km/h to 80 km/h

• Vehicle speeds increased for 3 of the 4 roads. Mean speeds increased by up to 9 km/h, while 85th percentile speeds, the speed below which 85% of drivers drive at, increased by up to 14 km/h.

• There was no clear trend detected in the levels of compliance with the posted speed limit.

(f) Freeways and Divided High Standard Highways Changed from 100 km/h to 110 km/h

• The level of compliance with the posted speed limit increased sharply, with the proportions of at-risk 'speeding' motorists (travelling at greater than 20 km/h above the posted limit) also reducing.

• Vehicle speeds increased by about 5 km/h.

• The application of 110 km/h had no effect on speed on existing 100 km/h roads

Source:VicRoads, Submission to the Inquiry Into the Revision of Speed Limits in Victoria, 30 September 1994, Appendix.

Last update January 11, 2002
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