Gravel, asphalt, concrete and paving can all be permeable. However, some types of asphalt and concrete are impermeable. This is why it’s important to be precise about what material you want for your driveway. If you want a permeable driveway, you should also make sure that your sub-base is also permeable.
Hertford is actually the county town of Hertfordshire, England, and it's a civil parish within the East Hertfordshire district of the county. Hertfordshire is situated in the south of England, bordering other counties such as Essex and Cambridgeshire. Greater London is in addition directly to the south.