A Guide to Vehicle Activated Speed Signs (VAS)
23rd June 2022
Vehicle Activated Speed Signs (VAS) are highly advanced, eye-catching signs used on both public and private highways across the whole of the UK. These devices have been proven to have a drastic impact on the road in regards to traffic calming and speed reductions.
The following guide aims to provide an overview of VAS. This will include a detailed explanation of what VAS are and how they work, a brief history of the development and implementation of VAS, and their applications.
What are Vehicle Activated Speed Signs?
Vehicle Activated Speed Signs are roadside LED signs which indicate whether or not an approaching vehicle is traveling above the road speed limit. There are 3 variations of VAS, each with slightly different functionalities; the Speed Limit Reminder (SLR), the Speed Indicator Device (SID), and the Smiley Activated Message (SAM).
The SLR is triggered by an approaching vehicle that is travelling above the speed limit of the road. The sign will then display the road speed limit inside a red circle with a “SLOW DOWN” message below.
Similarly, the SID will also display a “SLOW DOWN” message should a motorist be travelling above the speed limit, however the numbers above will reflect the exact speed of the approaching vehicle. The number will also be displayed if the vehicle is travelling below the speed limit, however the “SLOW DOWN” message will not appear.
The SAM also displays the speed at which any motorist is travelling. When detecting a speed below the limit, a green smiley face will illuminate below the displayed speed, and when detecting a speed above the limit, a red sad face will illuminate.
History of Vehicle Activated Speed Signs
“Speed sensing signs” were first trialled back in 1979 in Hampshire. Since then, continuous research and development has been conducted to improve and progress to what we know today as the modern VAS. Messagemaker Displays have been configuring and supplying state of the art VAS since 2011. Signs nationwide have since been required to conform to EN12966 in 2014, and must be designed to mirror the TSRGD standards, should they be permanently placed on a public highway. A huge emphasis has been placed on quality on the development of Messagemaker VAS, ensuring the most accurate and effective devices possible.
How do Vehicle Activated Speed Signs work?
There are three ways in which VAS can be powered; battery, solar or mains powered. In a battery powered unit, a lead acid battery within the device will feed into a charge controller, providing power to the device. On a full charge from a power cable plugged into a three-pin wall socket, the battery’s power will last around 45,000 triggers (one trigger= one vehicle causing the device to power on). A solar powered device will have the same lead acid battery however a solar panel mounted above the device will provide charge to the battery, which will then feed into the charge controller in the same way. For a mains powered device, a slightly different power supply unit (PSU, as opposed to a charge controller) is mounted within the device. This will then be connected to a constant mains power source, such as a roadside lamp post, through a weatherproof cable and convert AC 240V to DC 12V.
Once the charge controller or PSU has power, this will then power a central control board within the sign which will illuminate the LED’s and power a vehicle detection radar. As a vehicle approaches the device, the vehicle detection radar will send information back to the control board which will then illuminate the LED’s accordingly. For example, if a radar on an SLR device detects a vehicle travelling above the speed limit, this will then signal the device to display the speed limit accompanied with the “SLOW DOWN” message. The speed limit, display time of the appropriate message, and the maximum trigger speed at which the sign is configured to, can be programmed and adjusted using three simple internal dials.
What are Vehicle Activated Speed Signs used for?
VAS are predominately used to serve as bright and eye-catching visual reminders of speed limits and speed awareness for road users. Studies have shown that when motorists are made aware of their speed, this can lead to a reduction in speed and therefore accidents.
Furthermore, some devices can come equipped with data capture functionality, allowing the user to download and analyse data as recorded from vehicles triggering the device. The user will be able to establish trends in regards passing vehicles, for example peak times at which vehicles may be speeding. This can then be used to put in place further traffic calming measures, such as variable speed limits during peak speeding hours.
How do Vehicle Activated Speed Signs impact road safety?
As concluded from a VAS device in-situ with data capture functionality, speed signs are highly effective in reducing the average speed of a motorist on a given road.
Over a two and a half week period, following the implementation of a Messagemaker Displays VAS on a road in a local village, recordings were taken on the 1st September, 7th September and 17th September. Most notably, the average speeds and the highest speeds were analysed. The average speed reduced from 39mph, to 38.8mph, to 28.8mph respectively. The Highest recorded speed also fell from 61.8mph, to 60.4mph, to 46.6mph respectively.
The vast reduction in speed a VAS can facilitate can lead to wider implications on accident prevention and road safety in general.
Advantages of Vehicle Activated Speed Signs
As previously mentioned, the visual reminder of a vehicles speed or the road speed limit can vastly impact the vehicle’s speed itself. This then can lead to a reduction in accidents and an increase in road safety.
Furthermore, speed signs can also allow the user to download and analyse data of motorists on the given road, meaning specific trends, such as peak speeding times, can be established. This then can be used to increase knowledge of the given road and implement further traffic calming methods if necessary.
To find out more, check out our range below!