Note for others not familiar, if you go Hammersmith Tube Station to Shepherd's Bush Tube Station overland by bicycle then it takes five minutes, depending on traffic lights. That is actual five minutes, as in three hundred seconds.
Clearly both areas are larger than their respective train stations but the stations are representative.
To actually get a tube or other train between the two is not entirely direct, you would probably get on the wrong Hammersmith station at first (there are two), spend five minutes crossing the road to get to the other one. Then at the end a bus or long walk would be needed, so you would soon be in 45 minute territory.
The traffic can be mostly ignored if doing the route by bicycle except on the various mini ring roads they have to keep traffic deadly. Hammersmith itself is like a six lane motorway ring road of hell, easy to die on that one. Then at Shepherd's Bush there is that green bit where the traffic just goes round and round very slowly. On the bike you just go straight without getting sent around these merry-go-rounds of car fumes.
No idea why anyone would want to drive in such parts of London even though I have had to do it for work myself. It is not even driving, just slowly shunting along, blocking the way for 'serious' road users who care about their time and arriving promptly. As a cyclist I don't see myself as a serious road user, I assume those people in cars have more important journeys than mine so I am deferential to them. Yet, if being prompt matters to you and you do work in London, the bicycle is the only reliable means of getting from A to B in a dependably timely manner.
By that definition, those people in their posh cars, inching along, can't really be that serious. If they thought about it properly they would abandon their tin boxes or find better jobs. Travel by car is that silly in London.