2024. 12. 2. 11:40ㆍCivil Engineering in Australia/Road Design
O Vehicle Speeds on Roads(km)
> High : 90~
> Inter : 70~90
> Low : ~70
O Design Speed and Operation Speed
> 85th Percentile Speed (Operating Speed)
This is the speed at or below which 85% of vehicles travel under free-flowing conditions.
It reflects the actual driving behavior of most drivers.
> Design Speed
This is the speed used to determine the road's geometric features (e.g., curve radius, sight distance).
It is typically set at or above the 85th Percentile Speed to ensure safety.
> Posted Speed Limit
This is the legal speed limit displayed on the road.
It is usually lower than the Design Speed, often by about 10 km/h, to ensure a margin of safety.
O Side Friction
> The side friction factor (f) is a measure of the frictional force between the pavement and the vehicle tyre.
Desirable value : used on intermediate and high speed roads with uniform traffic
Absolute value : urban areas or mountainous terrain, driver are more discomfort, it has non-uniform graffic flow, permits the absolute values of side friction
O Max Superelvation
O Min horizontal curve raidous
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