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Sight distance is how far a road user (usually a vehicle driver) can see before the line of sight is blocked by a hill crest, or an obstacle on the inside of a horizontal curve or intersection. Insufficient sight distance can adversely affect the safety or operations of a roadway or intersection.
The design sight distance allows a below-average driver to stop in time to avoid a collision in most cases. Driver perception/reaction distance is calculated by: d PRT = 0.278 Vt (metric) d PRT = 1.47 Vt (US customary) Where: d PRT = driver perception-reaction distance, m (ft) V = design speed, km/h (mph) t = brake reaction time, in seconds
Stop line in Toyokawa, Aichi, Japan Give Way lines in the UK "Shark's teeth" yield lines (white isosceles triangles) as used in the US and many European countries. Stop and yield lines [1] are transverse road surface markings that inform drivers where they should stop or yield when approaching an intersection.
Stopping sight distance → Roadway sight distance – Request made 16 March 2012 by user:Triskele Jim using template:movenotice. Reason given by Triskele Jim is "Since this article discusses stopping, decision and intersection sight distance, I propose moving it to something like 'Roadway sight distance'."
Interchanges should be spaced at least 1 mi (1.6 km) apart in urban areas and 3 mi (4.8 km) apart in rural areas; collector/distributor roads or other roadway configurations that reduce weaving can be used in urban areas to shorten this distance.
The second case describes the relationship of horizontal sight distance on safe speed. It is the maximum speed at which a vehicle can come to a full stop before an object, with speed V i, can intercept after having emerged and traveled across the horizontal sight distance "d hsd". Urban and residential areas have horizontal sight distances that ...
[9]: 431–433 Another benefit of all-way stops is assurance that vehicles enter the intersection at a low speed and have more time to take heed of the traffic situation, [9]: 430 especially useful when sight distance is highly restricted. Some of the disadvantages associated with all-way stops are: Increased emissions of hydrocarbons.
The design speed chosen for a high-speed roadway is a major factor in choosing superelevation rates and radii of curves, sight distance, and the lengths of crest and sag vertical curves. Roads with higher design speeds require wider lanes , [ 2 ] sweeping curves, wider recovery areas, broader clear zones , steeper curve banking, longer sight ...