Waiting, Waiting

I often travel by public transport - both trains and buses - and often see people waiting to collect commuters from the trains. Many of these people in their cars leave the engine running while waiting. Don't know whether it's me or if I am just a grumpy old man, but surely they must be wasting fuel and causing some pollution while doing this.

I often think I would like to say something like when it's gone, it's gone, but always chicken out. Maybe it's me and the action of starting the car uses more fuel than leaving the engine running for 5 or 10 minutes, though I am not convinced of this.

Resource conservation is, in my view, an important part of sustainable living and any potential waste should be avoided.