A device for carrying road traffic on the Bangalore metro

A few of us were wondering the other day if it might be possible to carry road vehicles on metro rails.

A car is a machine with wheels that operates on certain flat surfaces, namely roads.

cars

A metro train is also a machine on wheels, but it operates on railway tracks.

metro

Roads tend to be very crowded, but not so the rails.  Long stretches of railway tracks go unoccupied most of the time.

So, initially, we felt that if we could put cars on rails using a suitable adaptor, we could move some 4-wheeler traffic off the roads.

Such an adaptor, it turns out, is easy to build.

car_holder

A cage with a roof with eyelets that allow the cage to be lifted, and wheel chocks that immobilize the car will do the trick.

Such a cage makes the car easily transportable and allows it to be lifted onto railway carriages or inaccessible parking spaces (say on the roofs of buildings).

Advantages

We calculated that a typical metro coach could hold up to 8 cars (a coach is 22 metres in length while cars are usually less than 5 metres in length, and you can stack two car cages one on top of the other).

So, 20 coaches could hold 160 cars.

Assuming a metro train frequency of one every 5 minutes and 20 car coaches, you would have an hourly capacity of 1920 cars.

Typical peak road capacities are around 1700 cars per hour per lane.

Since many central Bangalore roads are single lane roads, this could effectively double the traffic capacity at the city center.

Disadvantages

However, the plan would be hard to justify for the following reasons.

Each metro coach can carry a maximum of 300 passengers (if they are packed 6 to a square metre).  So the ticket for a car would be that of 40 passengers during peak hours.  I doubt anyone would pay so much to travel by car on a metro train.

The second problem is that metro coaches are prohibitively expensive.  Metro coaches cost upwards of Rs. 8 crores each.

Finally, a metro transport system is designed to serve a high density of passengers.  Those 20 coaches would have been of far greater service to commuters if employed to carry 6000 people instead of 160 cars.

So, it would make sense to add car-carrying trailers only after all commuter demand has been met, and only if the cost of car-carrying trailers turns out to be far less than that of passenger coaches.

Using such cages for parking also seemed like an interesting idea, but I feel that the cost of such a system might again be prohibitive (it’s cheaper in India to use a valet).

Anyways, it was an interesting thought experiment.

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