Dear Colleagues

Conventional traffic intersections with traffic lights (or stop lights) are mainly used in the USA; whereas roundabouts (or traffic circles) are favoured in Europe and indeed, Australia. What baffles me is that roundabouts are clearly simpler, safer and far better and yet traffic light-based ones are still the main choice in the ‘Land of the Free’ – the USA. Quite bizarre.

For some unaccountable reason, the KISS (Keep it Stupid and Simple) principle has obviously not been applied to the use of intersections with traffic lights. The US-based Myth Busters recently assessed the two types of intersections and confirmed the assertions above.

A Roundabout is Safe and Efficient
Statistics clearly show that where roundabouts replace conventional intersections, traffic delays have been reduced by 90% and accidents by up to 80%.

A conventional intersection has 32 vehicle ‘conflict points’ against that of only 8 for a roundabout. The lane capacity for a roundabout is a significant 1800 per hour (against that of a conventional intersection of 1300 to 1500 per hour).

As you could probably visualize, the angle of collision for a roundabout is fairly low (thus lower impact) as compared against that for a conventional intersection where it is 90 degrees (thus far higher impact accentuated by higher speeds).

Consider this on your Next Approach to a Roundabout
You are approaching a far simpler and indeed safer traffic connection. The return on investment for roundabouts simply based on the massive reduction in accidents is huge (estimated up to eightfold).

Interestingly, crossings with flashing lights are apparently one of the most dangerous intersections types with accident rates five times greater than for a roundabout.

Thanks to 101 Things I learned in Engineering School by John Kuprenas with Matthew Frederick.

Christina Baldwin words are probably relevant to changing from the one traffic system to the other: Change is the constant, the signal for rebirth, the egg of the phoenix.

Yours in engineering learning,


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