Types of Intersection at Grade
An intersection at-grade occurs where roads meet or intersect at the same level. The following are the three basic forms of intersections at grade:
unchannelised and unflared
unchannelised and flared
channelised (including roundabouts)
These forms of intersections apply to both rural and urban situations.
Unchannelised and Unflared intersections (Type BA)
This type of intersection is normally adequate where minor roads meet and where major road intersects with a minor road. In urban areas, many intersections remain unchannelised, sometimes for economic reasons, even though the volume of turning traffic may otherwise need special treatment. In such cases, traffic is often controlled by traffic signals or regulatory signs, such as STOP or GIVE WAY signs, on minor roads.
Unchannelised and flared intersections (Type AU)
Simple unchannelised intersections may be flared to provide additional through lanes or auxiliary lanes, such as speed- change lanes or passing lanes
Speed change lanes allow left or right- turning vehicles to reduce or increase speed when leaving or entering the through road without aversely the speed of through traffic.
Passing lanes permit through vehicles to pass on the left side of another vehicle waiting to complete a right turn at an intersection.
Channelised intersections (Type CH)
A channelised intersection is one where paths of travel for various movements are separated and delineated. Raised traffic islands, raised markers, painting markings and safety bars can be used for channelisation. A roundabout is a channelised intersection where traffic moves clockwise around a central island.
The layout intersection should be adaquately illuminated by street lighting or defined by reflective pavement markers, signs, etc.