BMW look to nautical tech to make bikes more visible to vehicle radar

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'Be Safe, Be Seen' is a message that’s been hammered home to motorcyclists but the growing reliance on high-tech safety systems in cars means simply being visible to the human eye might not be enough.

Radar is only just starting to appear on the most high-end of bikes, but the tech has been available in cars for years. Initially restricted to luxury vehicles, it is very much entering the mainstream, allowing a huge number of road users to offload some of the stress of keeping a careful eye on their surroundings.

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It’s not necessarily a bad thing. Radar can 'see' through fog and spray and won’t be distracted by changing the radio station. But the tech has downsides, particularly when it comes to bikes, as their small size and plastic bodywork means they’re far less effective than cars at reflecting radar waves.

The reflectors could make seeing bikes easier

The problem has existed at sea for years, where small, fibreglass boats are just as invisible to nautical radar as motorcycles can be to automotive ones, so BMW have looked to the solutions used at sea for inspiration.

As seen in a newly published patent application, BMW’s idea is to fit small reflectors on the extremities of a bike – notably the bars and the ends of the axles – to bounce radar waves back at the system which emitted them.

These reflectors are simply miniaturised versions of nautical reflectors seen on the mast of a yacht. They work on the principle of corner reflection. By putting reflective surfaces together at 90-degree angles to each other, forming a spherical array of three-sided open boxes, you create a device that will reflect radar waves directly back at their source, whatever angle they come from. It’s a simple, passive solution to the radar visibility problem.

Radar systems have been used at sea to help smaller boats

Bike firms are acutely aware that as motorists become increasingly reliant on systems such as radar, it’s important to make sure that bikes aren’t forgotten. BMW recently expanded their commitment to the Connected Motorcycle Consortium, a multi-manufacturer group, also including Honda, KTM, Yamaha Suzuki and Triumph, which is developing a host of systems focused on the idea of vehicles communicating between themselves and being 'aware' of the other vehicles in their surroundings.

The patent shows how even cheap, passive components that could easily be retrofitted to any bike could play a role in achieving that target.

Radar technology explored

Small reflectors could be fitted on the bars

Bar-mounted By fitting four or six radar reflectors – on the ends of the bars and the bike’s axles – its ‘visibility’ to radar is vastly increased

Double benefit As a useful side-effect of their position on a bike’s extremities, BMW’s patent says the reflectors double as sacrificial, impact-absorbing bar and axle protectors

Metallic coating: BMW’s patent says the reflectors can be made of metal or, to save weight, be plastic or carbon-fibre with a metallic coating

Harder to spot Bikes are harder than cars for radars to see. In the words of BMW’s patent "Due to of the narrow cross-section these vehicles have a small backscatter area... This makes it difficult and/or delays the detection of vehicles."

A marine radar reflector

Size matters Existing marine radar reflectors are at least a foot in diameter due to the type of radar they need to reflect. The bike-mounted versions can fortunately get away with being much smaller and still reflect the radars used on cars

Suzuki system BMW aren’t alone in thinking along these lines: Suzuki have also filed a patent application for a very similar radar reflector system


On the radar: How Battle of Britain technology is appearing on 2021’s motorcycles

First published on 12 November, 2020 by Ben Purvis

The system emits a fan-shaped signal of high-frequency radio waves and senses their reflections

Acronyms have long been a familiar way for bike firms to crow about tech but long before terms like SRAD or DCT became familiar on two wheels the term RADAR – RAdio Direction And Ranging – had been coined.

Dating back to the 1930s and famously used by the RAF to fend off the Luftwaffe, radar’s use has spread from the military to civilian world and now is finding its way into vast numbers of cars and, from 2021, motorcycles.

Why? To let bikes fitted with the systems build a real-time picture of their surroundings, monitoring other vehicles in the vicinity and enabling technologies including Adaptive Cruise Control (ACC) and blind-spot monitoring.

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The radar sensors are made up of two main components: a transmitter and a receiver. The transmitter emits high-frequency radio wave 'chirps' in the 77GHz spectrum along a focused, fan shaped pattern.

These waves bounce off anything they hit inside that area, reflecting back to the receiver. By measuring those reflections – their width, the direction they came from and the time it took for them to return – the radar 'sees' objects, including registering how fast they’re moving and in what direction.

The Bosch-developed radar sensors that are first to appear on in motorcycles – with Ducati’s Multistrada V4 and BMW’s R1250RT having the system as an option in 2021 – can 'see' around 120 metres in front of the bike with a field of view of about 60 degrees. The Ducati also gets a rear radar with a shorter range to monitor vehicles approaching from behind.

The radar sensors themselves are just part of the system, though. The picture they build is useless without the ability to interpret it, and that requires all the information that’s become available to motorcycle computer systems in recent years thanks to inertial measurement units, so the bike knows how fast it’s going, its lean angle and rate of acceleration – allowing it to compare those with the objects the radar senses to tell how they’re moving in relation to the bike.

The systems only work with a specific speed range – between 30kmh and 160kmh. Because they are set not to turn on at lower speeds, they can be programmed to ignore stationary objects such as lamp posts or parked cars that might otherwise interrupt or confuse the system.

Close cooperation between the radars, IMU, ABS system and electronic throttles means that when the ACC is engaged a bike fitted with the system can maintain a constant distance – selected by the rider – from the vehicle ahead, accelerating and braking (gently) to keep pace with it and return to the preselected cruising speed when the road ahead is clear.

Because so much of the kit needed for ACC is already in many modern bikes, the system isn’t a vast additional expense. BMW’s front-only radar is a £500 add-on for the R1250RT, while Ducati’s front-and-rear system adds around £700 although it can only be had with £1250-worth of other kit at the moment, making it a £1950 option.

Rear radar will also feature on motorcycles

Radar technology explored:

  • Display and controls Buttons on the left-hand bar controls let you activate the ACC system and select the distance you want to keep from vehicles ahead, shown on the dash.
  • Rear radar Bosch’s rear radar is smaller than the front one, with less range, and monitors blind spots. Unlike ultrasonic blind spot monitors (as on BMW’s C650 scooter), the radar monitors the speed differential from vehicles approaching from behind. It activates with the indicators, illuminating warning lights in the appropriate mirror if there’s a vehicle in the blind spot.
  • ACC computer Bosch’s system merges this with the ABS computer, which is already connected to the IMU, speed sensors and the electronic throttle.
  • IMU Needed so fan-shaped radar signal doesn’t pick up the road surface when you turn into a corner. The radar range is also reduced when you lean over, so the system is programmed not to accelerate if the vehicle in front drops out of its field during a corner.
  • Front radar Emits a fan-shaped signal of high-frequency radio waves and senses their reflections. Multiple measurements every second mean that interference, for instance from other bikes or cars with similar radars, can be filtered out.


Keep your distance: BMW to launch radar-guided cruise control

First published on October 16, 2020 by Ben Clarke

BMW will put radar cruise control on bikes in 2021

BMW have joined the list of manufacturers working to release a radar-guided cruise control function for motorcycles. Following Ducati’s announcement that they will be first to market and spyshots showing a similar system used by KTM and BMW themselves, the Bavarian brand have released details of how their system will work.

The Active Cruise Control (ACC) system has been developed with Bosch and will allow the rider to set not only a cruising speed but also a distance from the vehicle ahead, which is detected using a radar sensor at the front of the bike.

The radar unit uses this information, plus yaw rate and current vehicle speed to calculate the likely path the motorcycle will take in the next 100m and then, if necessary, modulate speed.

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A required adjustment is sent via the bike’s CAN bus to the ABS, which can add revs to the engine or apply the brakes depending on what is needed.

Both the distance to the car in front and maximum vehicle speed can be set in three stages at the touch of a button and will be displayed on the dash. ACC features two riding modes, comfortable or dynamic, which alter how aggressively the bike accelerates and decelerates.

Radar technology will feature on bikes in 2021

The system also incorporates ‘curve speed control’, which manages your speed in a turn to maintain a ‘comfortable lean angle’. As you lean further, the bike limits its interventions to avoid unsettling the rider.

This feature will also prevent unexpected acceleration while you are leaning in a bend if, for example, the radar loses sight of the vehicle ahead (BMW say the radar’s capability is limited while you’re cornering).

The system doesn’t respond to stationary vehicles, either, so if you are approaching the back of a queue of traffic you have to do your own braking.

Expect BMW R1250RT models to feature the tech in 2021

If the system is unable to operate, a symbol on the dash will let you know that you are in full control of your bike. There is also a second warning to let you know you are in a situation where emergency braking may be necessary because the braking capabilities of the system are limited for safety reasons.

BMW say that the rider will take an active role in the effectiveness of ACC by riding in the centre of their lane, making lane changes and overtakes clear (the system reacts to the use of indicators) and adopting a calm riding style.

BMW haven't confirmed when the system will arrive, how much it will cost or which models will receive this technology but mock-up images from BMW feature their touring K1600GT model.

Watch our video review of the existing BMW R1250RT below:

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Ben Purvis

By Ben Purvis