When we drive around Chennai, it is so easy to get lost in the big infrastructure gaps and almost forget the smaller regular loses! Anna Flyover is a classic example, the place has been a point of traffic convergence and intersection for 2 high density corridors in Chennai has a signal that operates day in and day out for 365 days. If you have been here at 1 AM in the night(that’s when we do our road geometry survey), you still have people driving around! like there’s no night. Anyways to the point of my post, ‘how much does it take to justify investment in a solution’
We were stunned ourselves when we saw the numbers, Anna Circle intersection costs Chennai Rs 273000 / day! in petrol, human capital and ecological loss! Also take a look at the other major intersections we studied:
Tidel Park: Rs 246000 / day
Teynampet Junction: Rs 213000/ day
Chetpet Junction: Rs 283000 / day
Velachery Junction: Rs 183000 / day
If we are able to get the loss of various intersections, we might just be able to prioritize which corridor to work on first! As part of the project, we are trying to reduce the wait time at this intersection.
how we calculated it?
cost model since there are many models available to compute the intersection delay cost depending on the country and the level of service, we adopted a more simple approach and also the most conservative! (loss valuation at the minimum compared to other models)
since the study is for an intersection and not a grid at this stage, we have avoided taking queue length, instead we have taken the vehicle crossing in the signal time. the assumption also being made that the vehicles assuming 30 cars that crossed the signal actually waited at the signal! instead of being the lucky few who get the drive by! so we are adding a downward scaling factor so that we we average out the number of vehicles waiting constantly. subsequently we have taken the red signal time and taken the actual number of vehicles waiting. once the vehicle numbers are arrived, it is just multiplied by the signal time and loss/sec and number of cycles/ hour to arrive at the hourly loss.
variables taken and assumed explanation
- Idling is taken at 1.51 lit/ hour for car (IAA standard for 1200 cc) and 0.75 lit/ hour for 2 wheelers (bajaj website)
- Bus is calculated as a car! (so the loss actually would be much higher) and likewise autos are calculated as 2-wheelers – the P.C.U conversion was not adopted.
- Individual movement tracks are considered instead of composite movement. so from GN chetty all the waiting traffic was divided by 3 to get individual direction numbers. (Cathedral + Anna salai + NH Road
It is assumed that when a signal gets green, all the vehicles that cross the line waited at the signalSince all vehicles at the red signals waiting at a signal wait for different times, a final factor of 0.75 is added to the final loss value, based on the observation that 75% of the vehicles wait the entire signal period. (Side observed – NH Road -> Cathedral )
- The car idling usage is for a 1400 cc car.
- The annual income of people taking this intersection is assumed at INR 4,00,000 (based on the cost of ownership – asset value model) (i.e if a person owns a car of 4 lakhs his annual salalry should be 4 lakhs+ for him to get a loan for that car)
- The ecology cost is based on the carbon credit valuation
- The current signal times are based on a single time screen. (we are working to multiple time observation, so more accuracy can be expected in the next few days)
- Cost of per litre petrol is taken as INR 50.00 (which is already a 2% lesser assumption) –
for calculation it is taken that all cars and bikes are petrol based.subsequently, diesel vehicles are taken at the national sales percentage of 45% of all car sales. rest is taken as petrol. (no cng & hybrid for now!) – Cost of Diesel is INR 36.00
- We have finally added a 0.75 reducing scaling factor, to accommodate the fact that all vehicles don’t wait the entire red signal time. (this is done based on observation on tidel park)
- We know that the decimals are annoying! but we had to prove we are engineers this side after all
- Peak time is taken at 6 hours a day (i.e 7-10 AM & 6-9 PM) & off peak traffic is assumed at a straight 50% of the peak time load.
- All cars are assumed to be A/C cars
a note to the readers: if you think you can use this data to arrive at the intersection loss by any other formula, we would like to hear from you. please get in touch with us.
we are working on other junctions in Chennai. will update in this series.