Lane Keeping Assist

We have just replaced our 15 year old VW Touran diesel with a T-Cross 1.0 TSi. This is, as all new cars, fitted with lane keeping assist. I was wondering what would happen if it got confused? Could I, or my wife, fight it and win. Looking at the Bosch variant it either uses the electric power steering, if fitted, or brakes individual wheels using the ESP.

“Lane keeping assist uses a video camera to detect the lane markings ahead of the vehicle and to monitor the vehicle's position in its lane. If the vehicle’s distance to the lane markings falls below a defined minimum, the system steps in. In vehicles with electric power steering, it gently, but noticeably countersteers in order to keep the vehicle in the lane. In vehicles without electric power steering, it achieves the same effect by utilizing the electronic stability program (ESP®) to brake individual wheels.

Drivers can override the function at all times, so they retain control of the vehicle. If they activate the turn signal in order to intentionally change lanes or turn, the system does not intervene.”

I am fairly happy with these various assist systems so long as the appropriate risk assessment and performance level calculations have been carried out, so not designed like the Boing anti stall system.


Some while ago I started a thread on EVs apparently becoming immobilised due to battery or other failures.

The new car has a DSG transmission and the selector lever is locked in Park when the ignition is switched off. It requires 12V to be available to release it, so flat battery and the car is immobilized. Reading deeply in the handbook it can be released with a screwdriver (supplied with the car but buried under the spare wheel) by opening a flap in front of the (conventional) hand brake lever. Who, other than an Aspergers spectrum engineer, would actually look that up?

  • That was an interesting interaction of systems Rolling eyes  I guess that the car had an automatic transmission, otherwise disengaging the clutch to engage a suitable gear for the reduced speed would have turned off the cruise control.

    What would the correct algorithm for this situation be? If you had remained on the dual carriageway you would have expected the car to return to the preset speed when any obstruction went away (although maybe not at full throttle). How could the system determine that you had moved to a different situation?

    I have had a similar although not so scary situation. I had set the cruise control to 80 kmph when travelling through a reduced speed roadworks area. At the end I accelerated up to the speed limit, 120 kmph and continued on my way. At my exit I steered onto the exit ramp and decelerated. The speed dropped to 80 kmph and stayed there  Worried A quick dab on the brakes turned off the cruise control and all was well.

    I wonder what performance level, if any, is specified for these systems? If you are in vehicle with an automatic transmission and the cruise control remains engaged you have to hope that the engine stop button works (but maybe it is disabled when the vehicle is moving?) or that the brakes can beat the engine

    Maybe something similar took place here???

  •  I presume the car that reads the speed limit signs is is the solution to that, except that round here it needs to recognise that lamp-posts and no signs mean drop to 30. I can see how the situation arose, and once bitten twice shy - and to be fair to the car it was not a problem again - a large part of the issue was the strangeness of a hire car. (and I normally drive a car with manual gearbox, manual handbrake so I was slightly out of comfort zone already)

    Getting out of the situation only takes a second, but it is an un-nerving second.



    Different rules in Wales, street lights without speed limit signs means there's a 20 mph speed limit. 

  • There should always be a 30 MPH speed limit sign as you enter a 30 MPH zone, streetlights or not.  But you're expected to remember that once you're in that zone.

  • North Wales Expressway A55 dual carriageway, heading east. 

    What is the speed limit here for a commercial vehicle, such as a Transit van?

  • Transit is not a car-derived chassis, so presumably 60, or it would be in England. In Wales I assume 20 ;-)


  • Preceding it is a 50 mph section with a speed camera van often hidden on top of a high retaining wall behind a metal palling fence. 

    Further on it is signed as National Speed Limit. 

    So, do motorway speed limits apply in-between in this 70 mph section, are vans allowed to do 70 mph, because it's not National Speed Limit?

    My new car reads roadside speed limit signs and displays what it sees on the dashboard and is generally accurate.  But it doesn't alter the speed of the car, unlike higher specification versions of the car.

    This technology must surely cause all sorts of issues if installed in commercial vehicles?

  • Even better than lane keeping assist would be a "left lane assist" to put people back in the left lane where they should be when there is space, rather than them driving soporifically in the middle lane.  Any attempt to hint to them that they should move over is met with blank stare or abuse.

  • I do like the sound of that idea

  • I tried out the Lane Keeping Assist in the snow this weekend. I was a little nervous of how it would join in on a twisting snow covered mountain pass (Julier in this case). In general it was ok but got somewhat confused when the road became 4 black stripes on a white background. It also tried to follow the tyre tracks from the bus in front which swung to the left and then turned off right. Finally it announced that it was no longer available, leaving an orange warning triangle on the instrument display.

    Like my previous diesel the 1.0 TSI engine struggled to produce enough waste heat to warm the cabin. It took around 10 km at 80 km/h on a level road before the engine reached working temperature. That would be a significant battery drain for an EV.