Vehicle dimensions Normal steering deviations and tracking errors particularly

Vehicle dimensions normal steering deviations and

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Vehicle dimensions . Normal steering deviations and tracking errors, particularly of heavy goods vehicles, reduce clearances between passing vehicles. Higher truck percentages require wider traffic lanes. Vehicle speed . As speeds increase, drivers have less control of the lateral positions of vehicles, reducing clearances, and so wider traffic lanes are needed
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Lecture 6 13/04/14 8 DESIGN OF CROSS SECTIONS Determination of the Cross Section Elements Right of Way The right of way is the total land area required for the construction of the highway. Its width should be enough to accommodate all elements of the highway cross section, any planned widening of the highway, and any public utility facilities that will be installed along the highway. The desirable minimum right of way width for 2-lane urban arterial road is 25m. Traffic Lanes In principle, the number of traffic lanes may be obtained on the basis of the standard design service volume of 2000pcu/h/l. This is used to divide the expected daily volume of traffic (also expressed in pcu) to obtain the required working number of lanes. The final decision on the number of lanes, however, may be determined by economic and administrative considerations. E.G. Ceremonial road may have more lanes than required. In practice the minimum number of lanes is two. This is driven by safety and ease of traffic operation considerations. Lane widths usually vary from 3.00-3.65m. Most arterials have 3.6m lane widths. Overall, carriageway widths should be minimised so as to reduce the costs of construction and maintenance, whilst being sufficient to carry the traffic loading efficiently and safely.
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Lecture 6 13/04/14 9 DESIGN OF CROSS SECTIONS Shoulders A shoulder is that portion of the roadway adjacent to the trafficked lanes that is used primarily as a refuge parking area for distressed vehicles. Other functions of the shoulder include: To protect (laterally support) the road pavement Safety and comfort of operation. Parking off, emergency outlet for evasive action, ‘openness’ improves capacity and encourages uniform speeds Shoulders can be used for segregated non-motorised access Shoulders are provided on all roads regardless of their function, except minor access roads or mountainous roads. On Urban roads, except for arterials, this may not be clearly distinguishable Recommended width 3.35 for a lorry to park and to safely change tires. Passenger cars require less space and economics of construction is important, hence 1.0-3.0m usually recommended for highways. Shoulder type and condition is very crucial if they are to be used as outlined. Recommended slopes for shoulders are 2%-4% for bituminous and concrete- surfaced shoulders and 4% to 6% for gravel or crushed rock shoulders.
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Lecture 6 13/04/14 10 DESIGN OF CROSS SECTIONS Cross Slopes (Camber) Pavements on straight sections of two-lane and multi-lane highways without medians are sloped from the middle downward to both sides of the highway. This provides a cross slope, whose cross section can be either curved or plane.
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  • Winter '19
  • Mr. Zhu
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