NYC area driver here... TLDR the entire article but I'll give my first hand perspective to say that "T" (taxi) and "L" (livery) plated vehicles on the highways in the NY metro area DO significantly add to congestion as the drivers keep their speeds well under the limit while traveling in passing lanes. Frequently I see these non "cab" "T" and "L" vehicles that I assume are "transportation network" company contractors driving unusually slow because they're either on their mobile devices (looking for pickups?) or driving so under the limit that I assume to not break any GPS speed monitoring rules enforced by these "transportation network" companies, or just generally inept.<p>I'm not advocating speeding by any means, but after driving 500k+ miles in the NYC metro area you can spot the ineptness and/or driving under fear of speed monitoring of these "T"/"L" plated vehicles. All it takes is for one to be driving 45 mph in a 55 zone on a two lane road with an already congested merge ahead, or they travel in the left passing lane at speeds well under the limit preventing other motorists from advancing, or overall poor driving, then it's a chain reaction of braking and delays mounting behind them.<p>I've always assumed that the monitoring of these drivers adherence to speed limits is the reason why they travel noticeably slower than the average driver in normal traffic. If that's the case it unfortunately causes the average capable driver to become indirectly part of the "transportation network"'s speed monitoring resulting in delays for everybody.<p>In the relative absence of these "T" and "L" plated vehicles, I've driven in moderate to heavy volumes where the average speeds are in the 60-65+ MPH range. However, when the livery vehicles start to increase within similar volumes of traffic the average speeds seem to drop and the congestion related delays seem to increase.<p>So if you were to ask me "Do transportation network companies decrease or increase congestion?" My answer would be "yes". Why? Based on my observations, I suspect it's related to the speed monitoring of the "transportation network" company and a tendency of the drivers of these vehicles being inept relative to other non "transportation network" drivers.