The definition of V85
The V85 speed, or the 85th percentile speed is the speed that 85% of drivers do not exceed, and 15% of the drivers do exceed. The V85 speed therefore gives an indication of the typical speeds driven at a specific Telraam location. For example, if the V85 speed is 45 km/h it means that 85% of the cars drive with a speed of 45km/h or less.
V85 is not related to the speedlimit
Note that the V85 speed is not related to the actual speed limit. It can be (well) below it if the speed limit is high and other factors (such as traffic density, the surface quality, or visibility due to large number of bends, etc.) cause the speed of traffic to be dominantly lower. This is often the case on busy roads during rush hour. Conversely, V85 can also be (well) above the speed limit, for example in some Zone 30 streets where inadequately designed road infrastructure combined with the low traffic volume allow for higher speeds.
The V85 speed is - and has historically always been - a widely used indicator in the world of mobility and road safety, to check whether a speed limit is consistent with the road layout and environment. The V85 speed is considered to be representative of the speed that can be safely maintained on a given road.
Be careful with the interpretation of V85
It is important to place the V85 indicator in a broader context and to not only use this indicator as an indication of liveability. In order to reach policy decisions and interventions, it is important to draw conclusions based on different data (traffic intensities for different modes, average speed, road characteristics and function) and statistics (e.g. accident figures). Neighbourhood residents, experts by experience, are often well placed to identify specific issues. Those local insights, from a participatory approach are important to properly interpret the value of V85.
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