Lane monitoring with electronic horizon

Apparatus for a vehicle operated on a roadway having lane markers includes an optical sensor providing optical data of the roadway. A first lane model is stored in an electronic memory in response to detected lane markers in the optical data. An electronic horizon system tracks a position of the vehicle and provides roadway data in response to the position. A second lane model is stored in the electronic memory in response to the roadway data. A confidence checker compares a discrepancy between the first and second lane models to a threshold in order to determine a confidence level. An output selector selects the first lane model when lane markers are detected in the optical data, and selects the second lane model if the lane markers are not detected in the optical data and the confidence level is greater than a predetermined level.