Brief: On November 17, 2021, the official EU Intelligent Speed Assistance (ISA) regulation was published under the regulation number (EU) 2021/1958. The Intelligent Speed Assistance (ISA) is a system that prompts and encourages drivers to slow down when they are over the speed limit. 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), Among them, Speed Limit Information Function (SLIF) is an important part.

 
The article "INTRODUCTION OF EU ISA FINAL DRAFT REGULATION" on October 21 of this public account has introduced the technical framework and test requirements of the regulation.

DEFINITION OF SLIF
‘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.

SLIF DISPLAY
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. The perceived speed limit shall be displayed on the speedometer, or as a numerical value, using a symbol resembling a model of speed limit road sign referred to in the Convention on Road Signs and Signals, of 8 November 1968; or as a text consisting of the value and the unit of measurement.

 
In certain scenarios when no perceived speed limit is available to the ISA system, such as when road signs are partially obscured, rotated, missing or conveying divergent information such as maximum load, vehicle size, etc., the SLIF shall provide a dedicated optical signal to the driver clarifying this particular situation and displaying or not displaying an assumed speed limit indication. In case of an assumed speed limit indication on the SLIF, a question mark “?” shall be displayed prominently adjacent to the numerical value, the system shall also provide a subtle and not-annoying audible notification each time when the perceived speed limit changes.

 
SPEED LIMIT DETERMINATION
The SLIF shall be able to determine the speed limit within 2.0 s at the latest after the manufacturer’s declared reference point on the motor vehicle passes the road sign by observing both explicit and implicit road signs. For explicit road signs, the SLIF shall be able to determine the applicable speed limit through direct visual observation of road signs or other effective methods; for implicit road signs, the SLIF shall be able to determine the speed limit through observation of road signs and signals using all relevant ISA system inputs (e.g. camera, electronic map data).

 
SPEED LIMIT DETERMINATION REAL-WORLD DRIVING RELIABILITY
The SLIF shall determine the correct speed limit for at least 90 % of the total
distance and for at least 80 % of the distance driven on each of the three road types. This requirement for reliable determination of the applicable speed limit is fulfilled if the distance-based performance requirement is met in real-world driving.
TP_D = (d_correct/d_total) * 100 %
where:
d_total – total distance driven for test drive;
d_correct – distance driven for test drive where the applicable speed limit was correctly determined;

 
ENVIRONMENT REQUIREMENTS OF REAL-WORLD DRIVING TEST
1.The test drive shall involve driving on public roads and streets within the territory of the European Union, The test drive shall involve driving on urban roads and streets, non-urban roads, and motorways/expressways/ dual carriageways, where each of the three road types shall represent at least 25 % of the total distance of the route. The route shall be one consecutive route with the same start and end point, where any repeated parts of the route in the same direction shall not count towards the test distance.

2.The test drive shall involve driving in daylight and darkness conditions, where darkness shall represent at least 15 % of the total distance. 

3.The test drive shall consist of a test distance of 400 km. The test may be terminated earlier if the test distance exceeds 300 km and the performance ‘TP_D’ varied between ± 5,0 % within the final 50 km of the route when calculated on a continuous basis.

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