Delft has a city centre which is very largely de-motorised. As a result it is a lovely place to walk around and spend time - perhaps the most noticeable thing is just how quiet it is! The core to this seems to be a "low traffic zone" covering most of the city centre, with largely uniform restrictions. Enforcement appears to be by camera.
The basic restriction is that private cars are not allowed into the larger part of the city centre, with exceptions for people with limited mobility, for residents, for people getting married, and so forth:
"Delft’s city centre is a low-traffic area. This means that visiting cars are not allowed to enter and park within the city centre. If you need to drop off someone with limited mobility inside the city centre, you can request a day permit online. Cars entering the centre without this permit will be fined." (source)
Getting married in city hall? "You can park on the southern end of the city hall, next to the bluestone skirting. You are allowed to park here between fifteen minutes before the ceremony and fifteen minutes after the ceremony." (source)
Loading vehicles are allowed in, but only at restricted times:
"Freight vehicles are only permitted to enter the central area of Delft, including the Delft logistics zone within the city centre, with the appropriate exemption, and then only between the hours of 0700-1200 Monday-Friday; 0700-1100 Saturday; and 1000-1200 Sunday." (source)
It's hard to believe that until 2004 Delft's central market square was a giant car park. For some good before and after photos, see this Reddit post.
There are no restrictions on cycling in central Delft (at least that I could see), but the provision of high quality cycling routes around the city centre, and two key routes through it, mean that in most places there are quite low levels of cycling (at least relative to the huge numbers elsewhere).
Oxford should implement something similar in its city centre. Basically remove all non-essential motor traffic, with exemptions granted as necessary.