Expressway service area refers to a place specially for passengers and drivers to rest, and should provide parking lots, public toilets, gas stations, vehicle repair shops, restaurants and canteens, with an average distance of about 50 kilometers. The construction scale of service area should adapt to the future traffic growth.

(1) unilateral service area

Unilateral service area is also called central centralized service area. Its layout principle is to set up a service area on one side of the road, and all kinds of functional services are concentrated in one service area. Vehicles in the reverse lane enter the service area through overpasses or tunnels.

Because unilateral service area has some defects compared with bilateral service area, it is relatively rare. There are two common forms of unilateral service area: one is a large centralized service area, with external service facilities on one side of the road and refueling facilities on both sides of the road. There are many service areas in this form in Europe, which focus on large shopping centers, entertainment facilities, accommodation, catering and other functions.

Another small one-sided service area is mainly due to the terrain, which has its existence value in mountainous areas and areas that cannot provide enough construction space, especially in the planning and construction of small service areas and parking areas. One-sided service area can play a good role to some extent. The terrain in northwest China is complex, and in some special geographical environments, unilateral service area is an inevitable choice.

It occupies a small area, conforms to the characteristics of two-way vehicles, and can play a unique role in these special environments. In recent years, with the development of expressways, some scenic service areas have appeared.

(2) Bilateral service areas

The layout of double-sided service areas is the most common, and its layout principle is to set up service areas on both sides of the road, with the same service facilities and functional divisions on both sides.

Because the expressway is a fully enclosed two-way lane with a separation belt in the middle, the setting of double-sided service areas can provide vehicles in and out of their respective directions respectively; At the same time, the service areas on both sides are connected by overpass bridges or tunnels, so that the vehicle capacity and material allocation are optimized.

Bilateral service areas should be used in a good geographical environment, which is more reasonable, meets the requirements of convenient, fast and efficient use, and maximizes commercial effects. Visually, bilateral service areas can be designed in the form of the same layout or in different forms, echoing the natural landscape environment.