You get Annual Leave WEEKS (five of these) - one week start of January to mid March, one week mid March to end of May, two weeks summer from end of May until mid October, one week mid October to end of December. Some depots have only four weeks of annual leave weeks with the rest as 'floating days' or you can sometimes ask to 'float' one week into 'ad-hoc' leave (annual leave DAYS).
Your 'Annual leave WEEKS' are guaranteed time off. You are all in different annual leave groups for your weekly leave. These groups or blocks are each allocated certain weeks in the year. There is a rotation each year, so you'll know or be able to find out, what group you'll be in next year and the forthcoming years, and roughly what dates they'll be for.
You can swap any of your annual leave weeks with another driver, or ask to swap into a vacant week. If you want Christmas week off, there is usually a lucky dip style draw for it, and sometimes rules about if you can take part the next year if you won it this year - depends on the depot.
Annual leave DAYS - Each depot will be able to have a guaranteed number of drivers off each day on annual leave DAYS (separate to weeks). This number depends on a 'local agreement' with the company, and is based on the 'driver establishment' (the number of drivers there should be) at the depot.
Let's say you're at a depot and the number of drivers allowed to be on annual leave days is four. If you are one of the first four to apply for that day, you'll be guaranteed it off. If you're the fifth or sixth etc, you'll get it off only if there are enough spare drivers to cover the turns of duty when the daily sheet goes up for that day. Some companies take drivers who want to work a rest day into consideration as well as spare drivers to cover turns of duty for drivers who want leave.
Bank holidays. Some companies have bank holidays as a normal day and your number of days annual leave per year takes this into account.
Other companies you get 'booked off with pay' (so told to have a paid leave day - like everyone who works in a bank or office), or you get an annual leave day 'in lieu' if you work or were already off on a rest day on a bank holiday.
You can swap turns of duty or rest days with another driver, but you must both sign the routes and traction of each other's turns of duty, and both have twelve hours rest between finishing a turn of duty and starting the next one.
Some drivers have a regular swap, and swap weeks of work. Driver A will work his own mornings one week and Driver B's mornings the next week. Driver B will work his own afternoons, and Driver A's afternoons the next week, so they both get the shift they prefer.
Some drivers like nights and swap whatever weeks work they have in the roster for someone who doesn't like nights' week of nights.
The local union reps are known as LLR (Local Level Reps) or LDC (Local Departmental Committee). As well as annual leave weeks, amongst other things they (where it's not a normal day) do the roster or organise a rota for who will work bank holidays, check the driver's diagrams for the permanent timetable and engineering work - that they meet the terms and conditions for when and where breaks can be taken/walking times/change ends allowances/preparation times etc.
They will make suggestions to management to perhaps swap elements of work from one diagram to another to make the diagrams more palatable or more reliable.
They will compile the drivers link or rota, position rest days and which weeks are mornings/afternoons/nights and try to make the weeks on the roster as near to 35 hours as they can. They will position the spare turns with their 'datum times' which you can be allocated a running turn from within +/- xnumber of hours from, in the roster.
I've made their job sound easy.
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I should add, that if you are planning to work on the Great Eastern part of Abellio Greater Anglia or later Crossrail, that the vast majority of annual leave is/will be incorporated into the 'link' or rota, which I understand is 8 weeks (some of which are five day weeks with the missing rest day used in the following two weeks) followed by two weeks off. The two weeks are made up partly from 'missing rest days' from five day weeks, and annual leave.
Presumably you can swap a week of rest days for a week of work, and the driver you swap with returns the favour with a week of his rest days for a week of your work so it suits you both.