The car park construction will normally include a certain amount of excavation, which should be done in stages. For example, turf should be stripped and stored, followed by topsoil removal and storage, and then subsoil should be excavated to a depth to create the road and parking bays with the appropriate gradients for drainage. Roots, wood and other organic material must be removed. The rocky base material for the car park can then be laid out and rolled to a sufficient depth for the strength required. Hard rock, crushed and angular in form to include all sizes down from 50 mm (2 in.) to dust should be used. Then the surfacing is added, either the sealed paving or unsealed material, which will be similar to the base. Lastly, the preserved topsoil and turf can be used to cover excavated surfaces and to tidy up the road and bay edges. Zones where no traffic or materials storage is permitted should be fenced off. Care will be necessary in the vicinity of trees to be retained on site. Soil should not be built up around the bases of trees. The drainage should not seriously affect the degree of water received by the trees or alter the water table.
Excess excavated material can be used to make mounds (see ‘Vehicle control’ below), spread over areas to be grass seeded, or taken off site to be disposed of in an approved way.
In many areas the landform and open nature of the site are such that there is nothing to stop vehicles from being driven off the road or parking areas and into other areas. This is usually undesirable because it poses dangers to pedestrians, and causes damage to soil and vegetation. Access into the hinterland may cause all manner of problems. Visitors with four-wheel drive vehicles and motorcycles are often tempted to go beyond the car park, while ordinary cars may well be parked off the surfaced areas during busy periods. Where the natural terrain does not prevent such access, control devices are needed. All need openings sufficient to allow wheelchairs, prams and baby buggies through. Few will restrict motorcycles, but all will restrict cars and most all-terrain vehicles.
The following types are most commonly used.
(a) A plan and section of a poorly designed earth barrier. It is too symmetrical and angular in form. (b) A better-designed barrier, asymmetric, rounded and blended into the local contours. It also allows a way through into a picnic area beyond.