It seems tautological that uber/lyft would increase congestion. The one and only way it would not be true is if every single person who used the service had a previous option that they were readily utilizing. Though even there nonpassenger driving hours would probably cause a net increase in congestion anyhow. But I think it goes without saying that there are countless people that end up 'driving' far many more miles thanks to uber/lyft, myself being one of them.

In other words as you make transport more desirable, available, and affordable - congestion will increase. The natural retort against this is public transport, but route/time restrictions as well as other passengers will always pose a limit on both the desirability and availability of public transport, though it certainly tends to nail the third criteria at least.