Progressive Safe System: Technical  Specifications 

Blind Spot Information Systems (BSIS)

Requirements for fitting the Progressive Safe System:  Blind Spot Information Systems and Camera Monitor  Systems (CMS)  


This specification is aimed at aftermarket systems intended to enable the legacy fleet  to obtain an HGV Safety Permit. Vehicles already approved to UNECE Regulation  151 are considered to have a BSIS likely to be more effective than one designed for  this specification, and are therefore treated as compliant with this BSIS requirement.  

Vehicles which have lower levels of direct vision carry a greater risk of allowing  Vulnerable Road Users (VRU) to be hidden from view by blind spots in the critical  moments before a collision. Lower direct vision vehicles force the driver to rely upon  the use of six mirrors, which has a time implication in terms of reviewing multiple  mirrors, and a quality implication in terms of the smaller distorted image of a VRU  when compared to direct vision. This reduces the capability to use peripheral vision  to identify VRUs which is afforded by high direct vision. The detection and driver  warning elements of the Safe System required vehicles with low direct vision to have systems that inform the driver of the presence of VRUs in close proximity to the  vehicle and actively draw their attention to it. This aims to replace the information  that was not received in the form of direct vision. The Progressive Safe System is  intended to build on the Safe System and to reflect a higher level of safety ambition  in the same manner as improved requirements for direct vision with the new three star threshold. 

The technologies in the Progressive Safe System are not direct replacements for  greater direct vision so cannot and should not be considered as direct substitutes. A digital information or warning system is not as effective at allowing an alert driver to  see and correctly identify a VRU as being able to see them with the naked eye.  However, part of the benefit of a turn assist system is that it can detect VRUs at the  side of the vehicle some distance to the rear of the cab where direct vision is  impossible. A turn assist system may also be more effective than direct vision alone  at drawing the attention of an inattentive driver. These benefits would be applicable  even in vehicles with five-star direct vision. 

For a swift transition to Progressive Safe System technologies, the requirements set  out in the following sections have been tailored to both the UK and non-UK specific  environment in which they are designed to operate, and the performance of systems  currently on the market. These parameters make alignment with existing regulation  

challenging, in some cases requiring tough performance such as removing the  900mm dead zone directly adjacent to the side of the vehicle in Regulation 151,  thereby requiring detection up to the side of the vehicle. This performance-based target goes beyond UN Regulation 151 but is designed to reflect the types of 

collisions seen in practice in the UK and the technology identified and assessed  during the development of this specification. 

High-intensity warnings, such as loud audible or other attention-taking warning  signals during a driving situation are only justified if the probability for an imminent  collision is high. If high intensity warnings are frequently used in situations where the  driver is aware of the hazards and/or there is no urgent need for them to act, then it  can lead to annoyance, potential cognitive overload, and a lack of trust in the  system, and can result in alerts being ignored or switched off. A low intensity information signal (e.g., an amber warning light) can be activated earlier and more  frequently without annoying the driver, while still providing useful information to them.  For a turn assist system it is appropriate to place the information signal towards the  nearside of the vehicle. In addition to alerting the driver, the information should  provide some indication of the location of the hazard. 

The existing Safe System recommended that systems should only provide the  information signal to the driver in response to the presence of a VRU and not a car  or a piece of roadside furniture (unless a collision with those items was imminent). It  was not made compulsory at the time because few systems were available that  could achieve it. This is no longer the case. 


“Blind Spot Information System (BSIS)” means a system to inform the driver of the  presence of, or a possible collision with a Vulnerable Road User (VRU) at the near  side of the equipped vehicle. 

“Reaction time” means the time from when the information signal is given to that  when a driver has reacted to that information. 

“Nearside” means the side of the vehicle nearest to the pavement/road edge on a  typical bi-directional road with one lane in each direction. In the UK, the near side of  the vehicle is the left side. 

“Information signal” means a signal intended to inform the vehicle driver about the  presence of a nearby VRU close to the vehicle but not necessarily on a collision  course. 

“Bicycle” means a combination of a bicycle and rider. 

“HMI” means the Human Machine Interface and relates to how the system interacts  with the driver in terms of controls, settings, information and warnings. 

“Vehicle Master Control Switch” means the device by which the vehicle’s onboard  electronics system is brought, from being switched off, as in the case where a  vehicle is parked without the driver being present, to normal operation mode.

“Vulnerable Road User (VRU)” means an adult or child cyclist, pedestrian, e-scooter  rider, horse rider or motorcyclist.  

“Warning signal” means a signal emitted by the BSIS with the purpose of warning  the vehicle driver when the BSIS has detected an imminent collision between the  moving vehicle and a VRU in close proximity to the nearside of the vehicle. 

“Information or warning signal mode” means the method by which the information or  warning signal can be communicated to the driver. These can be: 

  • Visual – meaning a signal that is presented visually only, such as a lamp or  symbol 
  • Audible (Tonal) – meaning a signal that uses one or more continuous or  intermittent tonal sounds, such as a buzzer, horn, or beeping signal. • Audible (Speech) – means a signal conveyed by the spoken word • Haptic – means a signal that is conveyed by the means of the drivers sense of  touch and feel, such as a vibrating seat, steering wheel or pedal. • Multimodal – means an information signal comprising more than one of the  above modes. 

“Lateral separation” means the distance between the nearside of the vehicle and the  VRU, measured when the vehicle and VRU are parallel to each other before any  vehicle turn is commenced. The distance is measured between the plane parallel to  the median longitudinal plane of the vehicle and touching its lateral outer edge,  disregarding the projection of devices for indirect vision, and the median longitudinal  plane of the VRU minus half of the VRU width. 


Vehicles that are approved to UNECE Regulation 151 will be deemed to comply with  all of these requirements. 

All other vehicles shall be fitted with a Blind Spot Information System that meets the  performance requirements set out below. This will be required for the benefit of  cyclists but is strongly recommended for pedestrians and other VRUs where  possible. 

Functional requirements 

The Blind Spot Information System shall inform the driver about nearby VRUs that  might be endangered if the vehicle were to turn so that the driver can choose not to  make any turn until it is safe to do so. 

It shall also inform the driver about approaching VRUs while the vehicle is stationary  before the VRU reaches the vehicle front, considering a driver reaction time of 1.4  seconds.

When the Blind Spot Information System identifies that a collision is imminent, for  example if the vehicle turns toward the VRU, then it shall warn the driver, by means  of a different and more urgent warning signal. When a vehicle and a VRU are  travelling in the same direction on a parallel path to each other, they can continue to  do so for an infinite time without collision even if they are in close proximity. This  situation does not constitute an imminent collision. 

The information signal shall not deactivate as a result of the vehicle turning away  from the VRU trajectory as long as a collision between vehicle and VRU is still  possible, in the event that the driver steered back towards the VRU trajectory (i.e.,  where a vehicle first swings out to the right to make room for a subsequent turn to  the left). 

The system shall be “active” and able to issue information signals and warnings  irrespective of the activation status of the direction indicators. 

The system shall be activated (or reactivated in the case of failure) upon each  activation of the vehicle master control switch. The default status shall be switched  on with every key cycle with the system remaining active when the ignition is  switched on. 

Information signals shall only be given for moving objects whose speeds, trajectory,  or other identifiable characteristics (such as size, shape, movement, or combination  thereof) indicate that they are a VRU. 

The number of false-positive activations due to the detection of static non-VRU  objects in near proximity such as cones, traffic signs, hedges and parked cars shall  be minimized (see section covering assessment conditions for false positive tests).  However, a warning signal is permitted if an imminent collision with a static object  has been detected. 

Performance requirements 

The BSIS shall be active at all vehicle speeds between 0 km/h and 30 km/h for all  ambient lighting conditions above 15 lux. It shall detect VRUs including bicycles of all  typical sizes and designs at all bicycle speeds between 5 km/h and 20 km/h. 

The BSIS shall provide information signals whenever it is active and a VRU is  detected within the range shown in the diagram below: from the nearside vehicle  edge (taken at the widest point, excluding mirrors, auxiliary equipment and super  structures above the height of 2m from the ground plane), to 2.2m lateral distance  from the vehicle, ranging from the front left corner of the vehicle to at least 9m rear of this point, according to the diagram:

The system shall also be capable of providing collision warnings whenever it is  active and a VRU is detected, and the system calculates that a collision is imminent  based on the trajectories of the vehicle and/or the VRU.  

Human Machine Interface Requirements 

The blind spot information signal shall be a visual signal that is clearly noticeable and  easily verifiable by the driver from the driver’s seat. This information signal shall be  visible in daylight, including in direct sunlight, and at night without causing disabling  glare or distraction to the driver. 

The device displaying the optical information signal shall be located at the near side  of the vehicle at a horizontal angle greater than 30° relative to an axis parallel to the  longitudinal median plane of the vehicle and going through the ocular reference  point. If the driver’s seating position is located on the near side of the vehicle, this  value may be reduced. 

If there is an increased risk of collision, for example the vehicle commences turning  towards a VRU that was previously travelling parallel to the vehicle path, a warning  signal shall be issued. The warning shall be a multi-modal signal comprising at least  

two of the following modes simultaneously: visual signal, audible (tonal) signal, or  haptic signal. Where any element of the warning signal uses the same mode as the  information signal, then the warning must be substantially different in presentation to  the information signal. For example, if both information and warning signals use a  visual signal, then the visual signal must look substantially different in respect of  colour, continuous or flashing behaviour etc. when used for information or for  warning.

It shall, at all times, be clear to drivers of vehicles if the blind spot information system is not working correctly, such as by means of an ‘error’ or ‘fault’ visual signal. 

The system shall display a permanent error in the event of restricted functionality, a  malfunction, (e.g., sensor failure or covering), defective information or warning  signalling, partial or complete failure of the system.  

Installation requirements 

The system shall be installed in such a way that it is not possible for the driver to  switch off the system, for example, no main electrical (on/off) switch should be  available to the driver.  

The system shall not adversely affect any safety critical aspect of the function or  performance of the base vehicle to which it is installed. 

Sensors or other means of detection, where the alignment or stability is critical to  successful operation in the defined zone, shall be mounted on structures th at are  essentially rigid and are not liable to movement or vibration in service. Mirror arms  that are adjustable in position shall not be considered suitable. 

No sensors, other means of detection, or other components of the system shall be  mounted such that they protrude in a manner that is liable to cause injury risk to a  VRU in the event of a collision, or conflict with the type-approval requirements for  sideguards, spray suppression or external projections. 


It is recommended that: 

  • Systems comply with as many of the requirements of UN Regulation 151 as  possible. 
  • When fitted to longer rigids or articulated vehicles, systems with a longer  rearward detection zone are used, such that information can be provided in  time to avoid collisions with a pedal cyclist at a point just ahead of the  rearmost group of tractor unit axles, at least when the speed of the pedal  cyclist is no more than 10 km/h in excess of the speed of the HGV (up to a  maximum cyclist speed of 20 km/h). 

Test procedure 

The manufacturer shall provide details of the basic design of the system and, if  applicable, how it is linked to other vehicle systems. The function of the system  including its sensing and warning strategy shall be explained and an operator’s 

manual/handbook shall describe how the operational status of the system is  checked, whether there is an influence on other vehicle systems, and the method(s)  used in establishing the situations which will result in a failure warning signal being  displayed. The documentation package shall give sufficient information for the test  service to identify the type of system and to aid the decision-making on the selection  of worst-case conditions. 

Assessment conditions (true positive tests) 

The tests shall take place on a flat asphalt or concrete surface. 

The vehicle sensors of the blind spot information system shall not be impeded in  their functionality by contaminants (e.g., ice/snow) or other means. 

Visibility conditions shall allow safe travel at the required travel speeds. 

The tests may be carried out in any load condition so long as the axle loads do not  exceed the limit specified by the vehicle manufacturer. The manufacturer shall  confirm that the function is available in all permissible load states. 

The vehicle tyre pressure shall be set according to the specifications of the vehicle  manufacturer. 

Static test 

The vehicle presented for testing shall be set up on a sufficiently large test area  ready to be driven off. 

The vehicle under test shall be secured against starting and rolling with the parking  brake system or additional mechanical means (wheel chocks etc). 

A VRU shall pass through the area covered by the Blind Spot Information System as  defined in the performance requirements section above, in such a way that the  movement is parallel to the longitudinal axis of the vehicle at speeds and lateral  separations described in the following table overleaf:




Lateral distance  from nearside  vehicle edge 


VRU type 

VRU speed 


500 ± 200  Cycle  7 ± 2km/h
1100 ± 200  Cycle  12 ± 2km/h
2200 ± 200  Cycle  18 ± 2km/h





Lateral distance  from nearside  vehicle edge 


VRU type 

VRU speed 


300 ± 200  Pedestrian  4 ± 2km/h
1100 ± 200  Pedestrian  4 ± 2km/h
2200 ± 200  Pedestrian  ± 2km/h


Compliance with the distance and speed specifications shall be demonstrated using  calibrated and traceable measuring equipment, markings on the test area and film  documentation. This can be done, for example, by determining speed using a GPS based measurement system and by observing the VRU path along defined  markings. 

The test is passed if the presence of the VRU is signalled by the BSIS in all test  cases for at least as long as part of the VRU is within the coverage area according to the performance requirements section. 

Signalling of the presence of the VRU shall be confirmed with cameras that can  determine the delivery of the signal and the respective position of the VRU alongside  the vehicle. 

This can be done, for example, by using synchronized video capture covering both  the internal VRU signal and the external position of the VRU on the test markings. 

Assessment conditions (false positive tests) 

The vehicle presented for testing must drive at a speed of 10 ± 2 km/h on a  sufficiently large test area through the centre of a marked corridor (width: vehicle 


width + 2 ± 0.1 m, length: 20 ± 0.1 m, distance between markings: maximum 5 ± 0.1  m, marking height: maximum 5 cm). 

A sign in accordance with BS EN 12899 1:2007(a) Fixed vertical road signs – fixed  signs) shall be attached at a usual height in line with the left-hand row of markings  (test setup see figure below). No other objects or VRUs should be in the covered  area. Care must be taken to ensure that the right row of markings and the traffic sign  are within the coverage area during the test. 

The test is passed if no information or warning signal is issued.