UK enforcement agency VOSA is using a combination of ANPR and weigh-in-motion technology to detect and target overweight trucks on some of the busiest motorways. Overloaded vehicles pose a potential danger to drivers, other road users and pedestrians.
Having identified a potentially overweight truck, VOSA liveried vehicles are used to alert the driver to the weighbridge (pic Road Transport Media)
UK enforcement agency VOSA is using a combination of ANPR and weigh-in-motion technology to detect and target overweight trucks on some of the busiest motorways.
Overloaded vehicles pose a potential danger to drivers, other road users and pedestrians. The additional weight can lead to catastrophic tyre failure, has a detrimental effect on the braking efficiency and increases mechanical wear. More mundanely, although perhaps equally expensive, overloaded axles impart considerable damage to road surfaces that cash-strapped road authorities can ill afford to repair. And yet the problem persists, so perhaps it is not surprising that overloaded vehicles are a key target for many of the world’s enforcement agencies.
In the UK, vehicles operating within the normal Construction and Use Regulations limit the maximum weight to 44 tonnes and allows individual axles to weigh of up to 11.5 tonnes (depending on the vehicle size and configuration). Enforcing weight limits is the responsibility of the Vehicle and Operator Services Agency (7524 VOSA) which is trialling a combination of intelligent systems to detect and prosecute overweight vehicles travelling on the main motorways and trunk roads.
Overloading is an ‘absolute’ offence in the UK and it has a policy to prosecute cases where overloading exceeds 30% and in the latest VOSA figures (2012/13) overloading was the fifth most common offence with goods vehicles. The figures also show that during the year 7,723 goods vehicles and coaches were taken for weight checks and of those almost 70% (5,388) were overloaded and issued with a prohibition notice. According to VOSA a proportion of overloading occurs due to ignorance of the rules or the vehicles’ capabilities, but there is also a proportion which is done deliberately for financial gain. Its policy is to target and weigh any vehicle it believes to be significantly overloaded. On normal carriageways and site visits this is relatively straightforward but trucks spend a large proportion of their time on busy motorways and trunk roads where identifying and intercepting overloaded vehicles can be difficult and potentially dangerous. While the inspectors use the visual appearance of a vehicle as an indicator of its load condition and condition, the Advent of air suspension systems on many commercial vehicles can mask any tell-tale signs of overloading. So to help identify overloaded vehicles on the motorways, VOSA is trialling a combination of weigh-in-motion (WIM) and automatic number plate recognition (ANPR) technology.
There are currently 10 of these WIM sites in England strategically located on the major road network including routes from the main ports and the M25 London orbital motorway. The WIM weigh sensors are permanently set into the road surface and are able to weight vehicles at traffic speeds, and the process starts by the ANPR identifying the vehicle’s registration number. For vehicles registered in Great Britain, the system searches various databases, one of which holds technical details including maximum weight thresholds. The permitted weights are compared against the actual weights as determined by the traffic speed WIM sensors to detect overweight vehicles or axles. Parallel searches reveal when the vehicle was last tested, if it has valid insurance and a current road fund licence.
VOSA also compiles its own operator compliance risk score (OCRS) database where vehicle deficiencies, fines and prosecutions are recorded against the operator. This enables officers to identify vehicles from fleets, both domestic and foreign, with poor maintenance records.
For foreign registered and other vehicles where there is no access to individual data, the axle and total weights are compared with the national limits or the class limits for lighter vehicles.
As the traffic speed WIM system is not accurate enough for prosecution, vehicles identified as potentially being overweight are intercepted by Traffic Enforcement officers in specially marked and equipped vans and escorted to the nearby VOSA station. The station contains a more accurate and calibrated low-speed WIM weighbridge as well as an area for vehicle inspection and a holding pen. Vehicles and/or individual axles which are overloaded by at least one tonne or 5% are subject to prohibition whereby the excess load must be removed before the vehicle is allowed to continue.
There are 75 dynamic axle weighbridges in VOSA estates although only ten locations have the WIMS/ANPR system which has been installed progressively since 2007. As a consequence the number of overweight vehicles identified by this technology is much lower at 1,529. However the agency says the pattern of overloading is rather random (although certain axle configurations are more prone to drive axle overloads) and involves vehicles in all weight categories so the WIM /ANPR combination enables it to effectively target its resources.
Once the vehicle is in the VOSA site, it is also checked for mechanical problems and the tachograph interrogated for drivers’ hours infringements. The agency highlights the effectiveness of the WIM/ANPR technology in identifying vehicles with multiple deficiencies which otherwise may have gone unapprehended.
Of the 1,529 vehicles the WIM/ANPR system identified as overweight, 251 also received a prohibition for mechanical defects while 164 were issued with a Drivers’ Hours prohibition. And almost 50 received all three prohibitions.
According to the latest report around half the heavy trucks weight checked were not registered in Great Britain and the foreign registered vehicles were more likely (62.7%) to be issued with a prohibition notice compared with 59.7% for the domestic fleet. While VOSA cannot impound foreign registered vehicles that are overloaded, it does prohibit and immobilise them until the overload is rectified and any fines are paid. All prohibitions involving non-UK registered vehicles are copied to the authorities in the relevant country
While a final conclusion from the pilot has yet to be drawn, the agency is planning to install WIM/ANPR at two further sites and is considering an extension to the system to remotely advise the vehicle operators of instances of non-compliance.
Here the technological fix is a number of robust and reliable retrofit systems now available for onboard vehicle weighing. Some commercial vehicle operators elect to install such systems either to prevent overloading while others utilise the technology to weigh the amount of product that has been placed in the body.
According to Keith Gresham, managing director of Axtec Weighing Systems, which markets both onboard and weigh in motion systems, one of the primary causes of accidental overloading is caused by the diminishing load effect. This is caused by the loss of the counterbalancing effect when removing part of the load from behind the rear axle. The effect is that the centre of gravity for the remaining load moves forward causing more weight to impinge on the front axle and producing an overload.
He says: “The concept that taking some load off a truck can cause it to become overloaded is counter-intuitive and may not even enter the driver’s mind. With an onboard weighing system they would be immediately alerted to the problem when they got back into the cab.”
Not only can these systems guard against overloading, Gresham says they also enable vehicle operators to utilise the full payload potential of their vehicles.
Central to the onboard weighing systems are load cells attached to either the body mounts (to weigh the product) or on stressed parts of the chassis/suspension for complete vehicle and axle weighing. Typically an onboard weighing system will be within ±5% on multi-axle trucks and ±2.5% on two axle vehicles and some manufacturers supply systems that can be extended to include semi trailers. Systems for measuring product will have a higher degree of accuracy but may not show the total vehicle and axle weights.
Inside the cab, the vehicle or axle weights will be displayed and a warning will be signalled as they approach the limits. In Axtec’s case the weights are usually displayed in green with the figures turning amber once the vehicle or axle is 80% loaded. If the vehicle or axle becomes overloaded the figures turn red and there is an audible warning (although this can be deactivated to prevent repeated activations due to load transfer when a vehicle is braking).
If a vehicle or axle remains overloaded for more than a minute a warning can be relayed back to the transport office via a tracking device and/or the information can be downloaded via an SD card. This enables transport and fleet managers to check either in near real-time or post-event, if a vehicle is or has been overloaded and therefore risking both a fine and the fleets’ licence to operate.
Overloaded vehicles pose a potential danger to drivers, other road users and pedestrians. The additional weight can lead to catastrophic tyre failure, has a detrimental effect on the braking efficiency and increases mechanical wear. More mundanely, although perhaps equally expensive, overloaded axles impart considerable damage to road surfaces that cash-strapped road authorities can ill afford to repair. And yet the problem persists, so perhaps it is not surprising that overloaded vehicles are a key target for many of the world’s enforcement agencies.
In the UK, vehicles operating within the normal Construction and Use Regulations limit the maximum weight to 44 tonnes and allows individual axles to weigh of up to 11.5 tonnes (depending on the vehicle size and configuration). Enforcing weight limits is the responsibility of the Vehicle and Operator Services Agency (
Overloading is an ‘absolute’ offence in the UK and it has a policy to prosecute cases where overloading exceeds 30% and in the latest VOSA figures (2012/13) overloading was the fifth most common offence with goods vehicles. The figures also show that during the year 7,723 goods vehicles and coaches were taken for weight checks and of those almost 70% (5,388) were overloaded and issued with a prohibition notice. According to VOSA a proportion of overloading occurs due to ignorance of the rules or the vehicles’ capabilities, but there is also a proportion which is done deliberately for financial gain. Its policy is to target and weigh any vehicle it believes to be significantly overloaded. On normal carriageways and site visits this is relatively straightforward but trucks spend a large proportion of their time on busy motorways and trunk roads where identifying and intercepting overloaded vehicles can be difficult and potentially dangerous. While the inspectors use the visual appearance of a vehicle as an indicator of its load condition and condition, the Advent of air suspension systems on many commercial vehicles can mask any tell-tale signs of overloading. So to help identify overloaded vehicles on the motorways, VOSA is trialling a combination of weigh-in-motion (WIM) and automatic number plate recognition (ANPR) technology.
There are currently 10 of these WIM sites in England strategically located on the major road network including routes from the main ports and the M25 London orbital motorway. The WIM weigh sensors are permanently set into the road surface and are able to weight vehicles at traffic speeds, and the process starts by the ANPR identifying the vehicle’s registration number. For vehicles registered in Great Britain, the system searches various databases, one of which holds technical details including maximum weight thresholds. The permitted weights are compared against the actual weights as determined by the traffic speed WIM sensors to detect overweight vehicles or axles. Parallel searches reveal when the vehicle was last tested, if it has valid insurance and a current road fund licence.
VOSA also compiles its own operator compliance risk score (OCRS) database where vehicle deficiencies, fines and prosecutions are recorded against the operator. This enables officers to identify vehicles from fleets, both domestic and foreign, with poor maintenance records.
For foreign registered and other vehicles where there is no access to individual data, the axle and total weights are compared with the national limits or the class limits for lighter vehicles.
As the traffic speed WIM system is not accurate enough for prosecution, vehicles identified as potentially being overweight are intercepted by Traffic Enforcement officers in specially marked and equipped vans and escorted to the nearby VOSA station. The station contains a more accurate and calibrated low-speed WIM weighbridge as well as an area for vehicle inspection and a holding pen. Vehicles and/or individual axles which are overloaded by at least one tonne or 5% are subject to prohibition whereby the excess load must be removed before the vehicle is allowed to continue.
There are 75 dynamic axle weighbridges in VOSA estates although only ten locations have the WIMS/ANPR system which has been installed progressively since 2007. As a consequence the number of overweight vehicles identified by this technology is much lower at 1,529. However the agency says the pattern of overloading is rather random (although certain axle configurations are more prone to drive axle overloads) and involves vehicles in all weight categories so the WIM /ANPR combination enables it to effectively target its resources.
Once the vehicle is in the VOSA site, it is also checked for mechanical problems and the tachograph interrogated for drivers’ hours infringements. The agency highlights the effectiveness of the WIM/ANPR technology in identifying vehicles with multiple deficiencies which otherwise may have gone unapprehended.
Of the 1,529 vehicles the WIM/ANPR system identified as overweight, 251 also received a prohibition for mechanical defects while 164 were issued with a Drivers’ Hours prohibition. And almost 50 received all three prohibitions.
According to the latest report around half the heavy trucks weight checked were not registered in Great Britain and the foreign registered vehicles were more likely (62.7%) to be issued with a prohibition notice compared with 59.7% for the domestic fleet. While VOSA cannot impound foreign registered vehicles that are overloaded, it does prohibit and immobilise them until the overload is rectified and any fines are paid. All prohibitions involving non-UK registered vehicles are copied to the authorities in the relevant country
While a final conclusion from the pilot has yet to be drawn, the agency is planning to install WIM/ANPR at two further sites and is considering an extension to the system to remotely advise the vehicle operators of instances of non-compliance.
Onboard weighing
Without a conveniently sited weighbridge to check their vehicles’ weights, many drivers and operators feel exposed to prosecution for accidental overloading and tend not to load their trucks to the limit. This leads to inefficiency in the transport operation as seven vehicles may be needed to transport goods that could be carried by six.Here the technological fix is a number of robust and reliable retrofit systems now available for onboard vehicle weighing. Some commercial vehicle operators elect to install such systems either to prevent overloading while others utilise the technology to weigh the amount of product that has been placed in the body.
According to Keith Gresham, managing director of Axtec Weighing Systems, which markets both onboard and weigh in motion systems, one of the primary causes of accidental overloading is caused by the diminishing load effect. This is caused by the loss of the counterbalancing effect when removing part of the load from behind the rear axle. The effect is that the centre of gravity for the remaining load moves forward causing more weight to impinge on the front axle and producing an overload.
He says: “The concept that taking some load off a truck can cause it to become overloaded is counter-intuitive and may not even enter the driver’s mind. With an onboard weighing system they would be immediately alerted to the problem when they got back into the cab.”
Not only can these systems guard against overloading, Gresham says they also enable vehicle operators to utilise the full payload potential of their vehicles.
Central to the onboard weighing systems are load cells attached to either the body mounts (to weigh the product) or on stressed parts of the chassis/suspension for complete vehicle and axle weighing. Typically an onboard weighing system will be within ±5% on multi-axle trucks and ±2.5% on two axle vehicles and some manufacturers supply systems that can be extended to include semi trailers. Systems for measuring product will have a higher degree of accuracy but may not show the total vehicle and axle weights.
Inside the cab, the vehicle or axle weights will be displayed and a warning will be signalled as they approach the limits. In Axtec’s case the weights are usually displayed in green with the figures turning amber once the vehicle or axle is 80% loaded. If the vehicle or axle becomes overloaded the figures turn red and there is an audible warning (although this can be deactivated to prevent repeated activations due to load transfer when a vehicle is braking).
If a vehicle or axle remains overloaded for more than a minute a warning can be relayed back to the transport office via a tracking device and/or the information can be downloaded via an SD card. This enables transport and fleet managers to check either in near real-time or post-event, if a vehicle is or has been overloaded and therefore risking both a fine and the fleets’ licence to operate.
