This used to be the main road from Hull to York and was much busier than today. The car park just down the hill was a gravel runaway vehicle 'stopping track' to prevent trucks with brake failure from going straight into Robert B Massey's Rolls Royce showroom.
The cache location is part of an old induction loop system to monitor traffic levels (before the days of digital cameras and AI). There are wires buried in the road that form loops or coils. Vehicles passing over affect the magnetic field and the system can log vehicle numbers, size, speed, direction etc.
Although old technology, these induction loops are still widely used today for barriers, traffic lights, and traffic monitoring.
Note: This is almost a nano.