i guess it's ok, as long as the authorities concerned have safety features properly in place.
something like stopping traffic at the source and waiting for the entire length of lane to clear, even before a single vehicle is allowed in.
the last time i saw them start one, we almost bumped the oncoming vehicles. there was no initial warning whatsoever. ni walang taong kumakaway!

the one in the early days of coastal road was good.
they wait for the last vehicle to pass, then they let the other direction thru.