I suppose you're looking for this:
# first query
a <- sqldf("SELECT VEHAGE, COUNT(VEHAGE) as count1
FROM veh
WHERE VEHTYPE==1
GROUP BY VEHAGE")
# second query
b <- sqldf("SELECT VEHAGE, COUNT(VEHAGE) as count234
FROM veh
WHERE VEHTYPE IN (2, 3, 4)
GROUP BY VEHAGE")
# combine
a <- sqldf("SELECT *
FROM a JOIN b
USING (VEHAGE)")