Add Interchange Ramps

Add Interchange Ramps
When the traffic flow at any road intersection at-grade (including signalised intersection) exceeds its capacity, the queue length of vehicles at the approach roads increases and the vehicles will have to wait for more than one signal cycle, resulting in increase in delays at the intersection.







One method to increase the capacity of the intersection and to reduce the delay is by increasing the width of the approach roads or adding additional lanes for a reasonable length of 50 to 150 m. As a result, there are at least three (or more) lanes on each approach leg of the road such that minimum of one exclusive lane each is marked and made available for left turn, straight and right turn movement of vehicles.

The left turn lane / lanes can be physically separated from straight and right turn lanes to enable free left turn movements of vehicles except during pedestrian crossing time.

Another method of increasing the capacity and reducing intersection - delay is by constructing grade-separator (fly-over or under pass). However, it is essential to widen the road approaches by sufficient width up to the required length (depending upon the ramp length) so that the vehicle and pedestrian movements are not adversely affected.

In order to make the grade separated intersection more efficient with lesser stopped delays, it is necessary to add ‘direct interchange ramps’ for free left turn movements and ‘indirect interchange ramps’ or loops for free right turn movements. If four such indirect interchange ramps for four right turn movements and four direct ramps for four left turn movements are provided at the grade separated intersection, a ‘Full Clover Leaf Intersection” is formed resulting in ‘signal-free’ and ‘stop-free’ intersection. Of course, this is the costliest option requiring considerable area and can’t be justified within urban limits of cities like Bangalore, except in specific cases.


Rs 1.2 crore saved!

BBMP claims that after the underpass at Cauvery junction was opened for vehicles, around Rs 1.2 crore has been saved indirectly.Well, this is how it works out.

According to Chief Engineer (Major Roads) K S Krishna Reddy, more than 90,000 two-wheelers and four wheelers pass through this junction everyday. Before the underpass was constructed, each vehicle had to stop for 180 seconds at the junction.

Now that the underpass has been constructed, there is no need to stop there. According to an BBMP estimate, the fuel saved which otherwise would have been lost either in idling the engine or starting the vehicle and changing gears is worth Rs 4 lakh per day.

It’s already more than a month since the underpass was inaugurated and the underpass has already saved more than Rs 1.2 crore !

EXPERT SAYS

Dr Justo answers some questions posed by Deccan Herald

What is your opinion on the trend of constructing pre-cast underpasses compared with the traditional underpasses ?

Use of pre-cast, pre-stressed concrete elements for constructing underpasses reduces the construction period considerably. This is a very great advantage. It is possible to design and construct underpass with pre-cast elements to be almost as efficient and as effective as conventional underpasses, provided appropriate steps are taken after conducting the required studies. It is necessary to adequately widen the approaches even if pre-fabricated elements are used.

As a case-specific instance for Bangalore, are such underpasses suitable for busy stretches as presently being taken up for connectivity to airport ?

Yes, it is necessary to conduct the required investigations and traffic engineering studies. Also the approaches have to be widened as per the traffic requirement.

Any suggestions on improving the proposed models?
A common design may not suit every intersection. Investigations and traffic engineering studies are to be carried out for each and every intersection and the design is to be made according to actual requirement.

Are there any alternative models of low cost underpass?, if any, please suggest.

The term ‘low cost’ can be often misleading, may be we can say, ‘cost- effective’. Alternate solutions such as steel structures can be planned.


By Dr CEG Justo,
Professor of Civil (Highway) Engineering (Retd.)
Bangalore University

Readers’ Remark


The technology will definitely solve the problem. But the way Palike is implementing it lacks futuristic vision. Everyday, more than 1,000 new vehicles enter the traffic in Bangalore. Considering the increase in vehicular population, the underpass constructed at Cauvery junction is insufficient.
It is too narrow. Palike should take up works keeping in mind the growth of the City in the next 10 years. The underpass at Cauvery junction may not be of much help in tackling traffic woes of the City after a year or two. As Palike has decided to use the same technology at other places, I appeal to th Palike to construct underpasses with more width.

K V Rajendra Kumar,
president, Peenya Industries Association


BBMP can’t go on widening roads to accommodate increasing vehicular population. Getting even an inch of land for infrastructure facilities is difficult. The government has to take up new projects within the available land. On the other hand, traffic density is increasing every day. Considering these facts, only solution to the problem is to have more underpasses. If pre-cast technology is used, it saves time and cost as well.

K P Abraham,
president ,Residents' Welfare Association Bangalore East
(REWABE)


The debate continues...

Our expert for today feels that ‘Full Clover Leaf Intersection’ is the best
solution in creating a ‘signal-free’ and ‘stop-free’ intersection as he explains in his write-up. Meanwhile, BBMP after some back of the envelope calculations has claimed that fuel worth around Rs 1.2 crore has been saved since the underpass at Cauvery junction was opened for vehicles. Readers continue to feel that the width of the underpasses are too
narrow but at the same time welcome the technology.


LEADER SPEAKS


Extend to other junctions

It is a good experiment by the BBMP. The Palike has succeeded in its experiment. As an institution, BBMP should always look for innovative ideas. This is one such technology which help the city in having better infrastructure facilities.

Whenever an experiment is taken up, resistance from all quarters is quite expected. BBMP officers should not have announced that they will complete the underpass at Cauvery junction in 72 hours. They should have completed the work within a short period without announcing any deadline. Then everyone would have appreciated BBMP. If Palike is implementing the same technology at other junctions, I welcome it. Of course since it is the first time, there is scope for further improvement.

While the work on underpass at Cauvery junction was going on, I visited the spot and discussed with engineers concerned. Then I expressed that width of the underpass is too less considering the traffic flow from Bhashyam Circle to Bellary Road. Then engineers disputed my opinion and argued that it was sufficient. Palike should relook into this. They should increase the width when they are implementing the same in other junctions.



Readers who wish to respond can e-mail their views to editor@deccanherald.co.in