Local authorities, and the Roads Service (in Northern Ireland), can choose:
You're made aware of these limits and conditions by means of road markings and signposts. In addition, parking meters or ticket machines have notices indicating the times when parking permits aren't required.
Metered parking bays are used to control parking on streets. If you park in a metered bay, you would need to pay for the period of time you parked there. Sometimes a maximum allowable parking duration is set, as well as a time period within which you're not allowed to return to the particular parking area.
Regardless of the presence of any road markings, it is an offence:
Local authorities, or the Roads Service (NI), issue blue badges for vehicles driven by or used for the carriage of disabled persons. You must display these badges in order to benefit from a disapplication or relaxation of the waiting and parking restrictions that apply to other drivers. It is an offence to use a disabled person's badge if you're not entitled to do so.
These are regulations where parking is generally not allowed at particular times (or even completely banned). Examples are yellow lines where vehicles can't be parked during controlled hours. In most places there'll be exemptions from the regulations, e.g. Blue Badge holders can park whilst clearly displaying their badge and clock. Additionally, loading or unloading is likely to be allowed (unless it is expressly banned).
Councils in England, Wales and Scotland, or the Road Service in Northern Ireland, can operate car parks that will also have regulations. They can provide for the type of vehicle that can use the car park, maximum length of stay, special bays e.g. Blue Badge holders, and places where vehicles can't park. In some car parks, contraventions of the regulations are enforced by Parking Attendants issuing Penalty Charge Notices (PCN). These can be challenged in the same way as if the PCN had been issued to a vehicle parked in the street.
Double yellow lines mean parking isn't allowed at any time. Councils, or the Roads Service (NI), don't need to put up a sign plate to accompany an 'at any time' restriction. In some areas, e.g. holiday resorts, the restriction can apply for only part of the year; although this must be for at least 4 consecutive months. In these cases, a sign, showing the duration of the restriction, will be put up.
A single yellow line on the road means that, at some time of the day, there'll be parking restrictions.
If the single yellow line is within a Controlled Parking Zone (CPZ), you can assume that it operates for the same time as the zone unless separate time plates show different times. A CPZ is an area where parking is restricted by Traffic Regulation Orders (Traffic Management Orders in London) according to with signs placed on all vehicle entry points to the area (except in designated parking bays or where otherwise signed).
For example, in a CPZ, which runs from 8.30am to 6.30pm, a yellow line without any separate time plates will be operational at those times. An exception to this rule is to allow a passenger to get in or out of the car; although you shouldn't leave the car unless the passenger is disabled and needs assistance or is a young child.
You mustn't park on white zigzags either side of pedestrian crossings at any time. The offence is different from other parking restrictions in that you would also get your licence endorsed (in Northern Ireland) or your electronic driver record updated (in the rest of the UK) with the details of the offence.
The yellow zigzags outside school entrances aren't enforceable unless there are accompanying signs indicating times they're in force. Where these exist, it's an offence to stop on them during these times.
Red, clearway or priority route networks can be found on major roads. These red lines mean that there can be no stopping on that route. The penalty is £60 and there is no discount. Red routes are enforced by the police's traffic wardens. This means that if you want to challenge a ticket, you have to attend a hearing at a magistrates' court.
While congestion charging doesn't compare with parking tickets, this is certainly something you'll need to think about in advance.
Cameras with number plate recognition software will note every car entering the charging zone. At the end of the day, number plates will be cross referenced against a database of payments made.