I spent some weeks last year trying to deter a pair from the vehicle - even driving it 40m away to the car park outside my gallery, but the robins kept finding it and carrying on with their construction! Eventually they stopped - only to then adopt the grill of the Landrover! I ended up grounding the vehicle for the entire nesting period, which in total was 38 days. It occurred to me after watching them stuff the front grill with leaves and moss, that these robins had probably adopted the most expensive nest box ever!
Still it was quite rewarding to then see the young chicks fledge from under the grill. It was quite amusing watching them neatly tucked away under the shelter of the car. The adult pair sat on the eggs for 17 days. It was difficult to see if any chicks had hatched as they were so tucked away inside the car. But one day the adults started following me around the garden until I put more food out for them. I knew this was a sign that the chicks had hatched as they needed extra food to feed their young. But whilst I enjoyed watching them, I need to be able to use my cars and can't really afford to turn them into nest boxes. So this year I was ready. As soon as I saw some interest in the back tyre of the Landcruiser I moved the vehicle and instead propped an old tyre onto the hedge next to where the Landcruiser had been parked.
So far they seem to like the idea and the tyre has been filling up with nesting material. Robins are famous for choosing all kinds of unlikely locations to nest in and seem unafraid of raising their broods amidst human activity. I've had them nesting in an old kettle in the garden before and even an old boot. This pair are so at home in my garden they have taken to perching on my wife's bicycle. I've stocked up on extra mealworms to offer them for once the eggs hatch!