Originally Posted by
emaij
My wife does not do well in cars so I'm thinking that we should take trains whenever possible. I have read that some of the track guage is small so that the trains travel slowly.
No, the mainline trains are all (very) wide gauge, they're just slow because they're... Indian trains. Travel by road isn't much faster, but is considerably more dangerous.
Distances in Rajasthan are long: for example, it's 12 hours by train from Delhi to Jodhpur, although the distance is fairly pleasantly covered overnight. You might want to consider taking the train one way, eg. Delhi-Agra-Jaipur-Jodhpur-Udaipur and then flying back.