Adap­tive cruise con­trol is not only use­ful, but also an im­por­tant part of the au­tonomous driv­ing puz­zle. How­ever, not all sys­tems op­er­ate in the same way. We put three to the test.

Popular Mechanics (South Africa) - - Contents - BY NI COL LOUW

We put four sys­tems through gru­elling tests to see which works bet­ter.

It’s early morn­ing out­side Bloem­fontein on the N1 and the fog is im­pen­e­tra­ble. If I drive too slowly, I risk get­ting hit from be­hind; up the speed and I might plough into the car in front. These are the kinds of con­di­tions where adap­tive cruise con­trol (ACC) can be a life-sav­ing safety fea­ture and, for­tu­nately, my Ford Kuga long-ter­mer is equipped with this use­ful tech. I set my speed to 80 km/ h and the fol­low­ing dis­tance to the max­i­mum set­ting. Not long af­ter, the Kuga slows and, sure enough, two faint rear lights ap­pear in the grey wall ahead.

While ACC was not in­vented pri­mar­ily as a safety net, it is clear that the tech­nol­ogy is an im­por­tant build­ing block on the way to fully au­tonomous driv­ing. We de­cided to put the sys­tems fit­ted to three of our long-term ve­hi­cles to the test.


Con­ti­nen­tal not only pro­duces tyres, but is also one of the big ACC sys­tems sup­pli­ers – it has sold more than 30 mil­lion radar sen­sors to au­to­mo­tive OEMS.

We re­cently chat­ted to Nor­bert Ham­mer­schmidt, Con­ti­nen­tal’s head of pro­gramme man­age­ment for radar, about the tech. Ac­cord­ing to him, be­cause it’s un­af­fected by ad­verse weather con­di­tions (in­clud­ing even the thick­est fog), the radar sen­sor is the most com­mon com­po­nent used in ve­hi­cles fit­ted with ACC from Con­ti­nen­tal. Radar: Con­ti­nen­tal radar-sen­sor tech is now in its fifth gen­er­a­tion and it is sup­plied as a pack­age in­clud­ing a pro­ces­sor and its soft­ware. This sen­sor op­er­ates at 77 GHZ and makes use of the Dop­pler ef­fect to iden­tify ob­jects with a rel­a­tive speed dif­fer­ence in a 65° ‘V’ fac­ing for­ward from the sen­sor, up to a dis­tance of 300 m. Early sen­sors could not op­er­ate at short dis­tances, which meant that ACC sys­tems did not work in stop/start traf­fic ( usu­ally slower than 30 km/ h). This type of sen­sor is a more cost-ef­fec­tive al­ter­na­tive and is still used in some ap­pli­ca­tions ( our Ford Kuga long-ter­mer is equipped with it).

Li­dar: This is an­other type of sen­sor that func­tions sim­i­larly to radar or sonar, bounc­ing a sig­nal off ob­jects and cap­tur­ing the re­sult­ing re­flec­tion, but uses laser light pulses where radar uses a ra­dio sig­nal.

Cam­eras: Subaru’s in­no­va­tive Eye­sight dual-cam­era sys­tem is the third type of tech­nol­ogy used. Our Subaru XV long-ter­mer is equipped with this and it also formed part of our eval­u­a­tion test­ing.

In­ter­est­ingly, in some ACC sys­tems, the radar sen­sors do not pick up solely the ve­hi­cle im­me­di­ately ahead, but may also ‘see’ the next ve­hi­cle in line as the waves move un­der­neath the first car. This in­for­ma­tion then feeds into the ve­hi­cle’s ACC al­go­rithms in case it needs to per­form an emer­gency brake ma­noeu­vre that may cause a chain re­ac­tion for the ve­hi­cles be­hind it.

These al­go­rithms are de­vel­oped to iden­tify tar­get ve­hi­cles as well as avoid­ing ‘ false de­tec­tions’, such as sta­tion­ary ve­hi­cles next to the road, as well as all the ap­proach­ing traf­fic in the op­po­site lane. Steer­ing an­gle is also one of the in­puts used to de­ter­mine the ve­hi­cle’s tra­jec­tory when, for ex­am­ple, you may be fol­low­ing an­other car round a bend in the road. As the sen­sor is con­nected to a ve­hi­cle’s CAN bus (the net­work link­ing to­gether all the elec­tronic con­trol units, in­clud­ing the en­gine con­trol unit), it can make use of ac­cel­er­at­ing and brak­ing to keep fine con­trol on the car’s speed.

Lo­cal min­i­mum fol­low­ing dis­tances are spec­i­fied by rel­e­vant au­thor­i­ties in the mar­kets where the ve­hi­cle is be­ing sold, as are all the re­quire­ments spec­i­fied by the man­u­fac­turer. Sup­plier com­pa­nies like Con­ti­nen­tal there­fore use their res­i­dent en­gi­neers to help cal­i­brate the sys­tem for any spe­cific sup­plier ac­cord­ing to all the le­gal and client re­quire­ments.


Ve­hi­cle man­u­fac­tur­ers of­ten boast about the peak power out­put of their en­gines, or the size of the in­fo­tain­ment screen, but lit­tle in­for­ma­tion is avail­able re­gard­ing the spec­i­fi­ca­tion of a ve­hi­cle’s ACC sys­tem. That’s why we put three sys­tems to the test and eval­u­ate the dif­fer­ences between them.


Three of our long-ter­m­ers stood out as the per­fect test ve­hi­cles, see­ing a Ger­man ( Audi Q2), an Amer­i­can ( Ford Kuga) and a Ja­panese ( Subaru XV) man­u­fac­turer tak­ing their places in the line-up. The Audi and Ford both em­ploy radar-based sys­tems; the Subaru, on the other hand, utilises the dual-cam­era setup.

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