Don't get me started on road design.
Traffic lights on roundabouts? I don't care WHAT mathematical model you've run (and I'm a mathematician), it's a load of junk if it thinks that putting traffic lights into a traffic flow does anything positive for traffic flow.
You can argue them for safety for pedestrian crossings.
But traffic lights are just a way of stopping 50% of the traffic dead still. If that's necessary for traffic to flow, you've designed your roads wrong. And if they are necessary on a three-lane roundabout, you have SERIOUS design problems that need fixing.
It's like having an Internet connection that, when your ISP is busy, they turn off 50% of their customer's packets for 60 seconds.