Just to expand on this, there ARE privately owned toll roads in Southern CA in the L.A. area. The price varies based on time of day and usage. This way, travelling on the toll road is "buying time" to avoid traffic, which is why you'd want to pay extra to use it. Charging MORE when traffic on the 'free' road is heavy is just good business, because it forms a basis upon which the traffic will be truly limited to a sane level on the toll road [making it ALWAYS a good alternative, not a traffic jam that you PAY EXTRA for].
What the analogy fails to cover is that, when it comes to the Internet, there are no alternatives: it's all toll roads. At best, you may have a choice between two competing roads, but there is no equivalent alternative of the 'free' road for Internet access.
That is why the analogy of different lanes on the road is by far the better one.
That said, the even more apt comparison is the one that the whole sticky issue arises from: the telephone service. In short, the FCC was created for the express purpose of regulating the then esssential telephone service so as to facilitate its role in fair interstate commerce. This was done along the same lines as the previous regulation of the rail lines, which were being abused to favour the owning states. (By charging out-of-state groups more to use the lines when passing through than their local groups were being charged to use the same lines.)
The point is that, like telephone services and train services before them, the Internet infrastructure is an essential utility upon which a great deal of trade is predicated upon and without which the economy would suffer greatly. The FCC's function, as it relates to Internet providers, is no different than it was when it dealt with phones: to ensure that the privately-owned, critical communications infrastructure of commerce is regulated in such a way as to provide fair and equal access.
Their express remit is to regulate the profit-seeking, 'capitalist' goals of these providers to ensure that those commercial interests are not allowed to run unchecked and thereby create advantages and disadvantages amongst the users of this essential infrastructure.