Road speeds: How vehicle data determines the v85 percentile and contributes to safer roads

The so-called v85 speed is one of the most important evaluation parameters for documenting driving behavior, as it represents the predominant speed level. This is the speed that is not exceeded by 85% of the vehicles recorded. Up to now, this speed in traffic has primarily been measured using spot speed measurements, although the disadvantages of this method are quite obvious. There are now far better ways of determining the v85 speed and other important parameters: Data from vehicles. We can provide you with essential traffic data from vehicles covering the entire German road network throughout the year. We support you in analyzing and interpreting this data in order to derive concrete measures.

Road traffic is becoming increasingly complex and requires innovative approaches to ensure the safety of all road users. The recording and analysis of driving speeds plays a central role in this. Thanks to modern technologies and the collection of data directly from vehicles, traffic speeds can now be measured more precisely and comprehensively than ever before. One key figure that is particularly important here is the so-called v85 percentile. In addition to the v85 percentile, we also determine the v75, v50 and v25 percentiles using the same logic.

What is the v85 percentile?

The v85 percentile is a statistical indicator that is frequently used in traffic planning and road safety. It describes the speed that is not exceeded by 85% of vehicles on a particular section of road. In other words, only 15% of road users drive faster than the v85 speed.

This indicator is particularly useful for understanding the general speed behavior on a road. For example, the v85 value is used to assess compliance with the speed limit in a 30 km/h zone. A v85 value of 33 km/h means that 85% of road users drive 33 km/h or slower and the other 15% of road users drive faster than 33 km/h. Traffic engineers, road planners and traffic authorities often use the v85 percentile to set speed limits and plan road safety measures. A speed limit that is close to the v85 percentile is usually appropriate and is perceived as safe by most drivers.

Traditional determination of the v85 percentile

Traditionally, the v85 speed was determined using permanently installed speed measuring devices or temporary traffic counts. However, these measurement methods only provided selective data, which was often not representative of the entire road section. There were hardly any comprehensive findings. In addition, these methods were unable to map the traffic flow over longer periods of time. The amount of data was limited and the measurements had to be evaluated manually.

Vehicle data: New approach to determining the v85 percentile

Advancing digitalization and the spread of connected vehicles have opened up completely new possibilities for recording and analysing traffic speeds. Modern vehicles are equipped with a variety of sensors and telematics systems that collect data on their position, speed, driving behavior and much more. This data can be collected anonymously and used to analyze traffic behavior.

By evaluating this vehicle data, traffic volumes and speeds can be recorded not only at specific points, but across the entire area. This allows traffic authorities to analyze speed behavior on different road sections, at different times of day and under varying conditions. In this way, the v85 percentile can be determined much more accurately than was previously possible using conventional methods.

Advantages of data acquisition from vehicles

Recording speed data directly from the vehicles offers a number of advantages:

• Continuous measurements: In contrast to traditional measurement methods, vehicle data provides more continuous up-to-date information. This allows speed deviations to be detected and analyzed more quickly.
• Broad coverage: As the data comes from a large number of vehicles, it can be collected across a wide area and over long distances. This allows a comprehensive analysis of the entire road network and not just at a few permanently installed measuring points.
• More precise analyses: The larger amount of data and the detailed recording enable a more precise calculation of the v85 speed. This means that speed limits and other measures can be even better adapted to actual traffic behavior.
• Long-term monitoring: With the vehicle data collected, traffic authorities can not only analyze short-term changes, but also identify long-term trends in speed behavior and react accordingly.
• Early detection of danger spots: By analyzing the speed at various points, dangerous sections where drivers are traveling at above-average speeds can be identified at an early stage. This enables targeted measures to be taken to reduce the risk of accidents[JW2] .

How does the v85 percentile contribute to road safety?

Knowledge of the v85 value is of central importance for traffic planning and increasing road safety. As it is based on the actual driving behavior of the majority of road users, it is a reliable basis for setting speed limits. If these speed limits are set based on the v85 percentile, most drivers will not feel encouraged to drive faster, which reduces the risk of accidents.

In addition, traffic authorities can analyze the v85 speed:

• Plan traffic calming measures: In areas where the v85 percentile is too high, measures such as speed reductions or structural traffic calming measures (e.g. traffic circles, speed bumps) can be implemented.
• Optimize traffic light control: If too many drivers are driving faster than the v85 percentile in certain areas, traffic control can be adjusted to make the flow of traffic safer.
• Introduce temporary measures: In situations with increased traffic volumes or particularly dangerous situations (e.g. roadworks), measures can be taken to increase road safety.

Precise speed data for safe roads

The collection of speed data from vehicles offers a revolutionary opportunity to determine the v85 percentile more precisely. This data is instrumental in improving road safety by enabling traffic authorities and other stakeholders, such as traffic engineers, to make informed decisions about speed limits, traffic calming and other measures. As the Safe Roads Initiative, we support the use of such technologies to make our roads safer and minimize the risk of traffic accidents.

Feel free to contact us and we will show you how you too can benefit from our digital tools!

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