Reshared post from +David Hembrow
The problem with that design is that drivers have to look in too many directions at once and because of this they are overloaded. Add a desire to get somewhere quickly, and also a chance that they're not paying attention, and the inevitable result is that crashes occur. It's a design which is the opposite of "fail safe" and is known to be dangerous.
The good designs look entirely different, and have far better safety records: