trevord:One answer would be to put some "advertise here from as little as £xxx per week, call 020 xxxx xxxx now" adverts on your rickshaws and see what response you get - I've seen that kind of poster on buses, in tube stations & in motorway service areas.
Brilliant advice.
Do it for all your rickshaws - it's free and depending on response you will know if it is worthwhile for businesses to do this on a paying basis.
I presume you already have a "to hire a rickshaw call 02 ......." Have a dedicated number for this, so you will know where the callers have seen the number. Thus if you have 100 rickshaws and get 20/40/100 calls a week to this dedicated number, then this is a statistic to tell potential advertisers that it is worthwhile.
David
Long ago, below an picture of a 4-masted sailing ship in a heavy storm was added: "A ship in a harbour is safe, but that's not what a ship is designed for"