• Friction

Introduction#

Thanks to Thomas Weber et al SUMO supports simulation of friction on streets since version 1.14.0 via network annotation and the friction device. This forces vehicles to reduce their maximum speed when they are on a slippery road.

Equipping vehicles#

To attach a friction device to a vehicle, the standard device-equipment procedures can be applied using friction as device name.

For instance, a single vehicle can be equipped as in the following minimal example

    <vehicle id="v0" route="route0" depart="0">
        <param key="has.friction.device" value="true"/>
    </vehicle>

Network modification#

The friction device will work with the lanes friction attribute, which defaults to 1 and can be modified either directly in the network or dynamically using traci/libsumo.

Vehicle Behavior#

A vehicle with a friction device will determine a perceived friction by adding random noise to friction coefficient of the lane and then calculate a new maximum speed for the lane by applying the following factor:

factor = -0.3491 * fric * fric + 0.8922 * fric + 0.4493

Parameters#

The following parameters affect the operation of the friction device.

• device.friction.stdDev: standard deviation when adding gaussian noise (default 1)
• device.friction.offset: constant offset to apply to all friction values (default 0)

All device parameters may be set via sumo option, vType parameter or vehicle parameter

TraCI#

Friction Modification#

Lanes support the setFriction and getFriction functions.

Parameter Retrieval#

Vehicles allow to retrieve frictionCoefficient (the perceived friction with noise), rawFriction (the friction value of the current lane), stdDev, and offset using the parameter API e.g. vehicle.getParameter(id, "device.friction.offset").