The original note, as written at the time
Congestion and traffic flow in general should be assessed on a lane per lane basis and the direction of movement should also be considered. This could ease the rerouting of ambulances and other emergency vehicles so that they can avoid the congested lanes.
Ongoing development
Congestion and traffic flow assessed lane by lane, with direction of movement considered, so that ambulances and other emergency vehicles can avoid the congested lanes.
The correction in the note is precise and it dismantles most traffic data. A road is not congested; a direction on a road is congested, and a lane on that direction may be empty. Average speed by road segment hides exactly the information an emergency vehicle needs.
Lane-level measurement is now cheap. Cameras and radar at junctions can count and classify, and the same infrastructure that enforces speed can measure throughput per lane.
The interesting consequence is routing. An ambulance does not need the fastest road; it needs the lane that is moving, which may be the wrong side of a divide, the bus lane, the shoulder. Lane-level data is what makes those choices legible.
The danger is that lane data becomes enforcement data. The same cameras can see a vehicle in a bus lane and issue a fine, and once the system exists for ambulances it will be used for penalties. That is worth deciding in advance rather than discovering later.
And a system that tells an ambulance which lane is clear should also tell the drivers, or the ambulance arrives to find the lane occupied.
Measure the lane, not the road. But decide, first, who may look.