Quote:
To provide for unimpeded, high-speed traffic flow is the general rule for the Autobahn design. Most Autobahns feature the following design elements (Unimproved older segments excluded)
-Two, three, or occasionally four lanes per direction.
-Rural section lanes are generally 3.75 meters wide except the left lane of newer three lane segments, which is 3.5 meters wide. On urban sections, all lanes are 3.5 meters wide.
-A landscaped vegetated median 3.5 or 4 meters wide (In urban areas, 3 meters). A double-sided guardrail runs in the middle. Blinders are often used on curves. Some newer sections have concrete barriers instead of vegetated medians.
-Outside emergency shoulders and long acceleration and deceleration lanes.
-Full grade separation and access control, generally provided by half cloverleaf interchanges at exits and full cloverleafs or directional interchanges at Autobahn crossings. Interchanges are generally well spaced, sometimes exceeding 30 km between.
-Grades of 4% or less. Climbing lanes are provided on most steep grades.
-Gentle and well banked curves.
-Freeze resistant concrete or bituminous surface.
-Roadbed and surface measuring about 68 cm (27 inches) in thickness.
Autobahns also feature the following amenities:
-Reflector guide posts at 50 meter intervals.
-Frequent parking areas, often equipped with toilets.
-Extensive and ample service areas featuring gas stations, restaurants, and hotels.
-Automated traffic and weather monitoring and electronic signs providing dynamic speed limits and/or advance warning of congestion, construction, accidents, and fog.
-Emergency telephones every 2 km.
-Pre-signed detour routes to facilitate emergency closures.
-Standardized signage.
-Wildlife protection fencing, crossover tunnels and "green bridges".
-Maintenance is superb. Crews inspect every square meter of the system periodically using vehicles with high-tech road scanning equipment. If a fissure or other defect is found, the entire road section is replaced. Barriers, signs, and other features are also well maintained.
http://www.german-autobahn.eu/index.asp?page=design
I am really quite impressed with the level of dedication in terms of roadway design, implementation and maintenance that Germany has put into the Autobahn system.