Method and control unit for adjusting a time gap

A control unit of an adaptive cruise control, ACC, system in a first vehicle, for adjusting a variable time gap (t) to be kept to a second vehicle, the second vehicle preceding the first vehicle, based on a road slope (α), wherein the control unit is configured for:

• determining a geographical position of the first vehicle via a positioning unit;
• determining a driving direction of the first vehicle;
• determining the road slope (α) of the road in front of the first vehicle in the determined driving direction;
• adjusting the variable time gap (t) based on the determined road slope (α) of the road in front of the first vehicle, the adjusting of the variable time gap (t) comprising:
• increasing the variable time gap (t) when the road slope (α) is negative, indicating downhill;
• or
• decreasing the variable time gap (t) when the road slope (α) is positive, indicating uphill, and
• determining the road slope (β) of the road at the determined geographical position of the first vehicle;
• wherein the variable time gap (t) in the control unit is further adjusted, based on the difference between the determined road slope (β) at the first vehicle and the determined road slope (α) in front of the first vehicle, by:
• increasing the variable time gap (t) when the determined road slope (α) in front of the first vehicle is smaller than the determined road slope (β) at the first vehicle;
• or
• decreasing the variable time gap (t) when the determined road slope (α) in front of the first vehicle exceeds the determined road slope (β) at the first vehicle.