ROAD JUNCTIONS OR INTERSECTIONS

ROAD JUNCTIONS OR INTERSECTIONS

Written by admin | September 13, 2012 | 0Edit

ROAD JUNCTIONS OR INTERSECTIONS

“The general term junction or intersection describes all roadway situations where two or more roads meet or cross one another at the same or different elevations.
The design and layout of road junctions demand careful considerations from the view pint of traffic management because it is very essential to have safety of vehicular traffic and pedestrians at such places

The factors to be considered while making selection for a particular type of road junction are as follows:

v  Availability of means of traffic control
v  Degree of traffic congestion
v  Funds availablev  Number of intersecting streets or roads
v  Volume and nature of traffic

The basic consideration in the design and operation of intersections must be the capabilities and limitations of the drivers, pedestrians and vehicles using the facility.
The general principles to be observed in the design of road junctions to minimize the risk of accidents are as follows:

• Angle of crossingAs far as possible, the acute angled junction’s should be avoided. The subsidiary roads should be made to meet at right angles to the main roads as far as possible.

• CamberAt junctions, the camber usually allowed is avoided and as far as possible, the whole area of the road junction should be done in one level

• ChannelizingThe road junctions should be properly channelized i.e. the number of conflict of traffic are minimized and lines of flow of traffic are made to cross at right angles or nearly at right angles. A properly channelized road junction permits right actions to do smoothly and makes wrong actions difficult

• Entry speedsThe road junctions should be designed in such a way that high entry speeds are discouraged.

• GradientIt is desirable to avoid change of gradient at the road junctions

• Importance of roadsIf road junction is meant for major roads and local roads, the latter should be carried under or over the former by subways or bridges respectively

• KrebsTo demarcate the boundary between the road and footpath, the kerbs are provided. They should be of suitable and should be made visible at night

• Pedestrians trafficFor road junctions having heavy pedestrian traffic, the hand rails should be provided adjacent to the kerbs with opening at pedestrian crossings.

• SimplicityThe road junction should be made as simple as possible. The rotes for traffic across the junction should be clearly defined and they should be obvious, especially if the driver is a stranger

• VisibilityThere should be ample visibility at the road junction. Each driver approaching the road junction should be capable of clearly seeing the vehicles coming from other directions. In that case only, he will be able to slow down his vehicle at junction, if found necessary.

The arrangements made at important road junctions can be divided into following three categories

• Traffic island
• Roundabouts or rosaries
• Grade separations

Traffic islands:

Junction

The space at a road junction over which traffic is not allowed to move is known as a traffic island
The arrangements at road junctions in the form of islands serve the following five objects:

• The efficiency of traffic handling is increased
• There is segregation of traffic in proper channels as they serve as guide to driver to negotiating the junctions
• The traffic island serves as shelter for pedestrians crossing the roads.
• The vehicles are compelled to move in one direction only and separate strips across the roads are provided for the crossing of pedestrians. Thus the chances of accidents are reduced
• They provide the proper place for the installation of traffic signs and other controlling devices

Traffic island  fig( a) 

Junction