Rollover of tractor/semi-trailer trucks is a serious concern by its human and financial consequences. No widely accepted method to prevent these harmful events has been found so far. A solution to this problem might be to detect and warn the operator on the center of gravity height of the heavy truck in on-road conditions.Estimating the center of gravity position of a vehicle while in motion may be a feasible approach, according to previous work. A more complicated problem is performing the estimation for a tractor/semi-trailer combination vehicle by measurements done on the tractor exclusively. The paper presents simple formulas which allow the above estimation for a minimal number of parameters and acquired data.Calculations done on the data describing the steady-state cornering of a real truck showed that an estimation with an error of about 20-22% of the center of gravity height by measurements done on the tractor vehicle exclusively seems possible. As the target of the approach in this paper is the driver's education by allowing him/her a better sense of the truck's rollover propensity and not the accurate measurement of the center of gravity height, the results obtained seem encouraging.