KATHIPARA CLOVERLEAF INTERSECTION, CHENNAI

SIDDHARTH AGARWAL32/11NEERAJ BANSAL14/11

TRAFFIC AND TRANSPORTATION SYSTEM

CLOVERLEAF INTERCHANGE 

It is a two-level interchange in which left turns (reverse directions in left-driving regions), are handled by ramp roads . To go left (in right-hand traffic), vehicles first continue as one road passes over or under the other, then exit right onto a one-way three-fourths loop ramp (270°) and merge onto the intersecting road.

When a freeway intersects a street or another freeway then a clover-leaf interchange has to be used. What it does exactly is that it allows a full non-stop access between any two busy roads so that the traffic can merge weave without actually having to cross at grade. So ,unless the interchange is too congested no stopping is required.

THE COLLOQUIAL OR PARTIAL CLOVERLEAF

It is almost same as the full cloverleaf except here the ramps are omitted.

Also a partial cloverleaf is preferred over a full one. In fact, in many places the cloverleaf's has been replaced with either signalized interchanges or High-capacity directional interchanges with flyovers.

The objective of a cloverleaf is to allow two highways to cross without the need for any traffic to be stopped by red lights, even for left and right turns.The limiting factor in the capacity of a cloverleaf interchange is traffic weaving.

Kathipara Junction is an important road junction in Chennai, India. Kathipara flyover is the largest cloverleaf flyover in the whole of Asia.

The junction used to be a roundabout and was the site of the statue of India's first prime minister Jawaharlal Nehru. A cloverleaf grade separator has been constructed as part of the NHDP to ease traffic congestion at the junction. The structure was built at an estimated project cost of ₹ 4,860 million with an initial deadline of March 2007. It is the first of three grade separators being built on the Inner Ring Road to improve connectivity between the various National Highways radiating from the city, the other two being the one on Koyambedu junction (NH 4) near the Chennai Mofussil Bus Terminus and the one at Padi Junction (NH 205).

The intersection consists of four roads meeting at a roundabout.

The four roads are

• Anna Salai leading to Guindy• NH-45 leading to airport• Poonamallee road• the Inner Ring Road (IRR)

The IRR and NH-45 carry substantial heavy traffic as this section acts as a thoroughfare and bypass for Chennai city.

Anna Salai leads to Guindy and is an important corridor in the road network of the city.

The Airport – IRR link has three lanes in each direction.

Anna Salai Road – Poonamallee corridor was raised to give headroom clearance.

There are four cloverleaf loops to handle right turning traffic and the left turning traffic will be undertaken at ground level.

TRAFFIC MOVEMENT DIRECTIONS

CHENNAI AIRPORTAirport to Guindy 1 – 11 – 4 – 9 – 13 Airport to Vadapalani 1 – 11 – 14 Airport to Porur 1 – 2 – 12 

PORUR :Porur to Guindy 8 – 9 – 13 Porur to Vadapalani 8 – 14 (side road) Porur to Airport 8 – 5 – 11 – 1 

VADAPALANI :Vadapalani to Airport- 14 – 11 – 1 Vadapalani to Porur 14 -11 – 7 – 12 Vadapalani to Guindy 6 – 13 

GUINDYGuindy to Vadapalani 13 – 9 – 3 – 11 – 14 Guindy to Porur 13 – 9 – 12 Guindy to Airport 13 – 10 – 1 

Now if you want to go round and round and take a complete circle :One full cycle 11 –4 –5 –11 –7 –3 –11

U - Turns at Kathipara Flyover :11 – 4 –5 –11 Airport side U Turn11 –7 –3 –11 Vadapalani side U turn8 – 5 – 11 –7 –12 Porur side u turn13 – 9 – 3 – 11 – 4 – 9 – 13 Guindy side U turn

DESIGN ANALYSISThe photo diagrams at right show close up views of the interchange, and the circled areas indicate entry or exit points.

At entries, to accommodate vehicles joining into the main road, the number of lanes should be increased for some distance to allow the traffic to merge in easily:

Number of lanes before entry + Number of entry lanes should = Number of lanes after entry.

For circled area 1, when 3 entry lanes join into 3 lanes, provision should be made for 3+3 = 6 lanes.

But we see only 4 after the entry.

Conclusion: • Traffic from 3 entry lanes is being squeezed

into a single lane, leading to a bottleneck. • Fast-moving traffic along the 3 running

lanes raises the risk of a serious accident. • In reality, this design allows for only 1 entry

lane.

Circled area ―4, conversely, has an extra exit lane.

Closer inspection will reveal numerous other flaws in lane markings and increasing/decreasing number of lanes in a short span of roadway.

When exiting a road circled area 2 lanes have to be dedicated for vehicles that are slowing to exit:

Number of exit lanes + Number of lanes after the exit should = Number of lanes before exit

For circled area 2, the number of lanes before the exit should be 3+2=5.

But there are only 3 lanes before the exit.

ConclusionThis indicates that traffic in only 1 lane (the lane towards the divider) would be able to move through without being hindered by exiting (slowing) traffic in the other 2 lanes.

PROPOSED MULTI MODAL INTEGRATION