Based on the context and the answer, generate a question. 

Context: They are able to travel up and down the country on a regular basis but again they have no guarantee of a having return loads . There are too many vehicles on the road which are being run inefficiently and without back loads . For the first Christmas ever internet shopping has overtaken the high street .

Answer:

There is no return load on the semi truck .



Why is it inefficient to run vehicles without back loads ?