A 12-car rally is a type of car rally

Rallying

Rallying, also known as rally racing, is a form of auto racing that takes place on public or private roads with modified production or specially built road-legal cars...

, often run by motor club

Motor club

Motor clubs are organizations, either for-profit or non-profit, which motorists can join to enjoy certain benefits provided by the club relating to driving a vehicle. There is typically an annual membership fee to join...

s as a simple and strictly amateur form of the sport.

12-car rallies are run to Navigational Rally rules, which are based on navigational skills rather than speed, and with usually a notable social element too. In the United Kingdom

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, the rules for 12-cars are governed by the Motor Sports Association UK (MSA) and are as follows:

• Maximum of 12 competing vehicles per event (hence the name)
• Generally only standard road cars permitted, not fully prepared cars (this is at the discretion of the organising club, but is widely upheld)
• Maximum 30 mph average speed only
• "Plot 'n' bash
  Plot 'n' bash
  Plot 'n' bash is a style of navigational information used on road rallies, where competitors are handed the route information at the start of each competitive section, just as the clock is started...
  
  " navigation only
• No timing to the second permitted, only to the previous minute
• "PR" (public relations) work as necessary if the route affects residential areas, this is as for a road rally but the requirements are not quite as strict
• Police to be informed of the event, though route information does not need to be submitted and approved
• Route authorisation must be granted from the MSA's local representative.