Dry, icy, snowy, or wet:
awareness of road conditions is a crucial safety factor as accidents in severe
weather arise mainly due to significant loss of friction between tyres and the
surface of the road. With its Road Condition Observer, Continental has
introduced a solution that allows road conditions to be classified with regard
to tyre/road friction.
A specific situation called
aquaplaning is extremely dangerous for manually driven vehicles as well as
automated ones. Technology company Continental has now begun to develop new
sensor-based concepts to warn the driver in the event of imminent loss of
friction. When there is a thick layer of water on the road, the water pressure
between the tyre footprint and the road surface can make the front wheels
float. Braking and steering are no longer possible, and the driver loses
control of the vehicle.
“Wet road conditions are
difficult for a car driver to evaluate,” said Bernd Hartmann, head of Enhanced
ADAS (Advanced Driver Assistance Systems) & Tire Interactions within the
Advanced Technology department of Continental’s Chassis & Safety division.
“Once you feel your vehicle floating, it is too late. Our aquaplaning assistance
concepts detect the early aquaplaning phase to make the driver aware of what is
going on under the tires. This can help drivers or automated vehicles to adapt
their speed appropriately to wet road conditions,” said Hartmann.
The system under development
is all encompassing – tyre, tyre-sensors, cameras, algorithms, brake actuation,
and the human-machine interface.
Predictive Aquaplaning Risk Recognition
Continental’s developers are
focused on predicting and managing the risk of aquaplaning. The objective is to
detect a possible front-wheel floating situation as early as possible in order
to trigger an early warning to the driver. Utilising signals from surround view
cameras and tyre-mounted eTIS (electronic-Tyre Information System) sensors, an
early warning concerning the approaching aquaplaning situation is provided to
the driver. Continental is also working on the control and stabilisation of
vehicles in aquaplaning situations, such as torque vectoring by individual
Aquaplaning conditions can also
occur unexpectedly with no opportunity for advance warning. In such cases, the
potential risk to other vehicles on the road can be mitigated by early
communication via V2X technology and eHorizon, facilitating a network of
solidarity where one vehicle acts as a safety sensor for all other vehicles and
not just those in its direct vicinity. eHorizon can provide this information to
vehicles that could potentially be affected, so they are able to adjust their
driving functions to the aquaplaning conditions.
Detecting an imminent loss of control through sensor re-use
To detect aquaplaning
situations, video images from surround view cameras mounted in the side
mirrors, the grill, and rear are analyzed. “When there is a lot of water on the
road, the camera images show a specific splash and spray pattern that can be
detected as aquaplaning in its early phase”, explained Hartmann. For example,
excessive water displacement in all directions underneath the tyre is a
characteristic attribute. During the first testing phase of the new solution,
the wetness recognition algorithms delivered a very high hit ratio in
predicting potential aquaplaning conditions.
In addition to image
information, Continental uses information from tyres to detect the risk of
aquaplaning. In this concept, signals from Continental’s eTIS sensors, mounted
on the tire’s inner liner, are computed. “We use the accelerometer signal from
the electronic-Tire Information System to look for a specific signal pattern”,
said Andreas Wolf, head of Continental's Body & Security business unit. A
tire model processes the incoming radial acceleration of the part of the tire
that is in contact with the road. For wet roads – when enough water is
transported out of the tread to ensure an appropriate grip – the signal shows a
As soon as a wedge of water
begins to form in front of the tyre footprint region and there is excessive
water on the road, the acceleration signal begins to oscillate in a
characteristic way, indicating an early risk of aquaplaning. Since the eTIS
sensor can also detect the remaining depth of the tire tread, a safe speed for
a given wet road condition can be calculated and communicated to the driver.
Testing has shown that future
aquaplaning assistance will also have the potential to intervene in an actual
aquaplaning situation by applying the rear brakes in a controlled way to
establish a degree of “torque vectoring” in order to maintain vehicle
maneuverability within physical limits.
Contribution to Vision Zero
Not only is aquaplaning a
challenge to the driver, but it is also difficult to pin down how many city
road and highway accidents in wet road conditions are caused by floating front
wheels. “This is one of the last blank spots on the strategic map towards
greater road safety”, said Bernd Hartmann. But drivers must continue to
consider a general rule: adjusting their speed to wet roads and keeping an eye
on the tyre’s tread depth. Since aquaplaning depends on tread depth, the height
of the water on the road and speed, Continental recommends renewing summer tyres
with three millimeters of residual tread depth. Below this limit, the risk of
aquaplaning increases significantly.
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