kind        effort    material   skill         where
   ----        ------    --------   -----         -----
   road         1,000   100 stone    125*         land province
* (optionally, Roadbuilding could be a new subskill of Construction)
Effect: building a road in a province reduces the base travel time to
any adjacent land province which also has a road by 2 days.  Thus, at
normal walking rate, plains provinces would take 5 days to reach, desert
and forest provinces 6 days, and mountain provinces 8 days.  Both
provinces must have roads for there to be any benefit.
A road contributes 0.25 to the civ level of its province for each
adjacent road province (thus, a maximum of 1.0 if all adjacent provinces
have roads).
                                        David desJardins