How to calculate the required torque or HP of single phase induction motor to carry a massive object?
Calculate separately the powers you need for 


acceleration (simple Newtonian physics) 
hill climbing (ditto, once you decide what speed you want up what gradient), 
rolling resistance (you'll need to research that, for the ground surfaces you're crossing. It depends on speed, ground surface, type of tyre, wheel size etc, you'll find plenty of info online to get you started)
Air resistance (again, some research needed, but you can estimate a Cd  and you know the frontal area from the bodywork design. Again there's plenty of info online)
Losses in the gear mechanism


Add these together and you have a minimum figure for the required power, you probably want to add 10% to 50% as a safety margin. (As you probably don't need full acceleration uphill, exercise judgment whetehr to add both of these numbers, or the larger of the two).

Torque (Nm) is simply power(W) / rotational speed (radians/second).
Torque at the motor for a given velocity obviously depends on wheel size and gearing.