When they first installed this contraption next to us, they messed up the incline. It was too steep so one of longer trailer trucks promptly got stuck on it ultimately doing just that - stopping all traffic on the highway. It was glorious.
Also, the speed limit on these bypasses is 60 km/h, so they are halving the bandwidth and create massive congestions during peak hours. Probably the reason they stopped using them recently and just close the highway for few hours at night instead.
Peak bandwidth of roads happens at surprisingly low speeds, you wanna maximise bandwidth set the speed limit to about 20km/h [1]. Anything higher and road capacity starts reducing.
So reducing the speed limit down to 60/h actually increases the capacity of the road, and reduces the likelihood of rolling traffic jams occurring or persisting.
This is a question I have wondered all the time (predominantly while stuck in traffic). Frequently wondered if, during rush hour, posted speed limits should be dropped by X to actually increased throughput.
Having not yet read the paper, I am curious if this was factoring in just typical average speed or if lower speeds are also going to have fewer/less severe accidents (accidents having an outsized impact on my road delays).
Bandwidth doesn't vary much with speed (since people tend to maintain the same 2 second gap from the car in front of them), except at low speeds where the nonzero size of each car becomes significant.
Anecdotally, it seems like I see more wild driving when posted speeds are higher. People are more aggressive in higher speed zones, which inevitably leads to more crashes. Severe accidents being one of those things which can dramatically hurt traffic throughput.
Also, the speed limit on these bypasses is 60 km/h, so they are halving the bandwidth and create massive congestions during peak hours. Probably the reason they stopped using them recently and just close the highway for few hours at night instead.