Some freeway entrances come in from the left instead of the usual right. why do these present problems to drivers entering the freeway?

Left side entrances present problems to drivers entering the freeway because of the following reasons:

1) Driver expectancy

2) Lane shifting

Explanation:

1) Driver Expectancy: Drivers are used to having ramps and accesses on the right side of the freeway, as the majority have been built that way until now. Changing this «general rule» may throw drivers off and confuse them, causing them to miss the exit or crash because they didn't expect traffic coming from the left side.

2) Lane Shifting: if not all exits are placed on the same side, this would mean drivers will have to shift from one side to the other to get to the exit. Crossing like that the "fast lane", with tends to have more aggressive drivers, would cause a mix of drivers that could be dangerous.

the factors that the economies of the muslim empires prosper were:

1- land trade routes-located between three continents  

2- sea trade routes

trade contributed to the spread of muslim empires, and with that islamic culture led to a growing feeling of internationalism resulted in the transfer of technology, science, and other cultural forms.