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The geometric design of roads is the branch of highway engineering concerned with the positioning of the physical elements of the roadway according to standards and constraints. The basic objectives in geometric design are to optimize efficiency and safety while minimizing cost and environmental damage.
Highway engineering (also known as roadway engineering and street engineering) is a professional engineering discipline branching from the civil engineering subdiscipline of transportation engineering that involves the planning, design, construction, operation, and maintenance of roads, highways, streets, bridges, and tunnels to ensure safe and effective transportation of people and goods.
Structural road design aims to ensure the road is strong enough for the expected number of vehicles in a certain number of years. The input of a calculation is the number expected of vehicles (e.g. 10,000,000) divided in groups (e.g. trucks, vans, cars) and the number of years that the road has to function before the road structure has to be fully renewed (e.g. 20 years).
Highway safety engineering is a branch of traffic engineering that deals with reducing the frequency and severity of crashes. It uses physics and vehicle dynamics, as well as road user psychology and human factors engineering, to reduce the influence of factors that contribute to crashes. A typical traffic safety investigation follows these ...
An Interstate Highway under construction , with both directions of traffic moved to one side of the roadway I-94 in Michigan, showing examples of non-interchange overpass signage in median, upcoming exit signage on right shoulder, a pre-1960 overpass with height restriction signage, newly installed cable median barrier, and parallel grooved ...
No standards currently exist for this design. The design depends on site-specific conditions. Additional signage, lighting, and pavement markings are needed beyond the levels for a standard diamond interchange. Local road should be a low-speed facility, preferably under 45 mph (72 km/h) posted speed on the crossroad approach.
Design speed is not necessarily road's maximum safe speed. As highway design incorporates a significant factor of safety, drivers can travel faster than design speed without difficulty when good weather conditions are present. [4] The highest design speed for a road or segment is the design speed of its least favorable part.
Stopping sight distance is one of several types of sight distance used in road design.It is a near worst-case distance a vehicle driver needs to be able to see in order to have room to stop before colliding with something in the roadway, such as a pedestrian in a crosswalk, a stopped vehicle, or road debris.