Not wishing to go completely off topic, but the residents managed for quite a few more than 1900 of those 2000 years as there wasn't random tinkering going on with road layouts.
If you close London Road completely you force the traffic from the Langford side of Bicester to go all the way around the bypass and back down Buckingham Road. At that point you used to be able to get into the town centre via North Street, but someone decided it'd be a good idea to close that - so instead you're carrying on further down the B4100 towards the A41 and A34 with all the other traffic (including those heading from Milton Keynes, etc to Bicester Village - whilst the signs try to send people around the bypass, satnav sends you the most direct route). Incidentally that section of the B4100 has recently been designated (or has been announced that it will be designated, to be precise) an Air Quality Management Area. Doesn't take a genius to figure out why...
If you were to go the other way around, you're on the A41 that runs behind Bicester Village, and then as The Planner said, you're stuck in the Bicester Village traffic coming off the A41 and eventually the A34/M40 flow. Yes there's signs that say 'car park full' everywhere, and a new shiny park and ride due soon, but again - satnav (and arrogant drivers) ignore signs.
Things are made worse at the moment by the weather, the increase in traffic to BV up to Christmas (and Black Friday is looming), and Launton Road - the former diversion route whilst London Road was closed - is closed itself. Guess where the official diversion route is? Yep, across the London Road level crossing. Genius.
Curiously enough, Google Maps still seems to be showing London Road being closed around the level crossing. Also, whilst it has been closed, people working in the office buildings near there have decided to use the road itself as a car park - which is annoying some locals.
Last but not least, there's been at least one 'crossing rage' incident, where, according to reports, someone saw the crossing start to close so decided to overtake a queue of stationary traffic and whiz under the barriers whilst they were closing. Not sure whether the CCTV was enough to get the licence plate...