● The Intelligent Speed Assistance (ISA) is a system that prompts and encourages drivers to slow down when they are over the speed limit;

● ‘Speed Limit Information Function (SLIF)’ means a function that is comprised of the speed limit determination system that determines the perceived speed limit, and a human machine interface that communicates the perceived speed limit to the driver; 

● ‘Speed Limit Warning Function (SLWF)’ means a function that alerts the driver that the speedometer speed is exceeding the perceived speed limit; 

● ‘Speed Control Function (SCF)’ means a function that attempts to limit the speedometer speed to a stable speed at or below the perceived speed limit;

● ‘Explicit numerical speed limit sign’ means an applicable road sign which shows a temporary or permanent numerical value;

● ‘Implicit speed limit sign’ means an applicable road sign which does not show a numerical value or shows a strikethrough numerical value.

Some of the road signs in the catalogue of road traffic signs in Annex II of the Regulation are as follows:

● The Intelligent Speed Assist (ISA) system shall comprise a speed limit information function (SLIF) and either a speed limit warning function (SLWF) or a speed control function (SCF). 

It shall be possible for the driver to manually deactivate the ISA system, either fully (i.e. the SLIF and SLWF, or SLIF and SCF), or partially (i.e. the SLWF or SCF). Automatic deactivation of the ISA system should be permitted where an automatic system (e.g. Automatic Lane Keeping System ALKS) controls the vehicle speed;

● The SLIF display shall display the perceived speed limit to the driver at least when the speedometer speed is more than the perceived speed limit, for speeds from 5 km/h or less, at the latest 2.0 seconds after the vehicle’s reference point passes the signs. SLIF should be able to determine perceived speed limit for the signs listed in Annex II of the Regulation. When no perceived speed limit is available to the ISA system, due to one or more circumstances such as road signs being obscured, missing or conveying ambiguous information, a dedicated optical signal, making clear this particular situation, shall be provided to the driver with or without an assumed speed limit indication on the SLIF. 

● The SLWF shall warn the driver for speeds from 20 km/h or less if the perceived speed limit is known and the speedometer speed exceeds it. The warning indication shall be provided by either “a visual warning + a cascaded acoustic warning/ haptic warning” or “a haptic warning alone”. The visual warning of “a visual warning + a cascaded acoustic warning/ haptic warning” or “a haptic warning alone” shall be provided within 1.5 seconds of the speedometer speed exceeding the perceived speed limit. The vehicle may be equipped with a means to suspend the SLWF.

● The SCF shall attempt to limit the speedometer speed to a stabilised speed by reducing the vehicle’s propulsion power and driveline torque, for speeds from 20 km/h or less. The SCF intervention shall start at the latest 1.5 seconds from when the speedometer speed exceeds the perceived speed limit. The SCF shall not actuate the vehicle’s service braking system except for vehicles of categories M1 and N1, where the vehicle’s service braking system may be actuated. An endurance brake (e.g. retarder) may be incorporated only if it operates after the SCF has restricted the propulsion power to a minimum. The deceleration rate of the vehicle shall be ≤ 3.0 m.s-2. 

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