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By Zoe Conway
Employment correspondent
As ambulance workers get ready to strike again, another anxious plea has gone out from the NHS: only call 999 if you really have to.
Wednesday's walkout will affect most ambulance services in England and Wales. The advice is to call 999 if you are seriously ill or your condition is life-threatening.
The action will involve thousands of staff, including paramedics, control room staff and support workers in a dispute over pay.
Action by teachers in Scotland also continues, with secondary schools being affected on Wednesday.
You can read more or watch this report about why people are taking strike action, and below you can find information on how it could affect you.
Which ambulance staff are striking?
Thousands of members of the Unison and GMB trade unions are walking out on Wednesday across most of England and Wales. The East of England will be the only service unaffected.
The start times and lengths of the walkouts vary between ambulance services, but most will last for about 12 hours.
The action will involve all ambulance employees, including call centre and control room staff, not just emergency crews.
Ambulances will still be sent to the most life-threatening calls - known as Category 1, which includes cardiac arrests. But it is up to each NHS trust in consultation with the unions to decide which calls are responded to.
- Call 999 If you are seriously ill or injured, or your life is in danger
- For all other healthcare needs, contact the 111 helpline, your local GP or pharmacy
- Attend appointments as planned. The NHS has said it will contact anyone whose appointment has to be rescheduled due to the strike
NHS medical director for secondary care Dr Vin Diwakar said: "The message from the NHS to patients is clear - if you need emergency care, please come forward.
"This means continuing to call 999 for life threatening emergencies as well as using 111 online for other health needs where you will receive clinical advice on the best next steps to take."
Upcoming strike action
THU 29 DEC
Rail disruption continues
- Staff at West Midlands Trains (WMT) and Great Western Railway (GWR) are on strike until midday
- This includes staff working in ticket offices, station management and guards
Border Force strikes
- Some Border Force staff are striking in England, Wales and Scotland meaning delays are likely for people arriving in the UK
- Birmingham, Cardiff, Gatwick, Glasgow, Heathrow and Manchester airports, and the port of Newhaven, will be affected
Driving test centre strikes
- Some driving examiners are on strike in the East Midlands, West Midlands, east of England and parts of London
- The industrial action will not affect theory tests but might have an impact on practical exams
FRI 30 DEC
Possible road disruption
- Some National Highways traffic officers are on strike in the West Midlands and south-west England
- The strike involves control centre staff and traffic officers who deal with the aftermath of accidents
Border Force strikes
- Some Border Force staff are striking in England, Wales and Scotland meaning delays are likely for people arriving in the UK
- Birmingham, Cardiff, Gatwick, Glasgow, Heathrow and Manchester airports, and the port of Newhaven, will be affected
Driving test centre strikes
- Some driving examiners are on strike in the East Midlands, West Midlands, east of England and parts of London
- The industrial action will not affect theory tests but might have an impact on practical exams
SAT 31 DEC
Possible road disruption
- Some National Highways traffic officers are on strike in the West Midlands and south-west England
- The strike involves control centre staff and traffic officers who deal with the aftermath of accidents
Bus drivers on strike
- Bus drivers in London are taking industrial action
- The routes affected are mostly in south and west London
Border Force strikes
- Some Border Force staff are striking in England, Wales and Scotland meaning delays are likely for people arriving in the UK
- Birmingham, Cardiff, Gatwick, Glasgow, Heathrow and Manchester airports, and the port of Newhaven, will be affected
Driving test centre strikes
- Some driving examiners are on strike in the East Midlands, West Midlands, east of England and parts of London
- The industrial action will not affect theory tests but might have an impact on practical exams
SUN 1 JAN
There are currently no national strikes planned for this date
MON 2 JAN
There are currently no national strikes planned for this date
TUE 3 JAN
Rail disruption continues
- The National Union of Rail, Maritime and Transport Workers (RMT) are on strike
- The RMT strike will affect services in England, Scotland and Wales and people are being advised to avoid travelling if possible
Read more: What are the train strikes about?
Possible road disruption
- Some National Highways traffic officers across England are on strike
- The strike involves control centre staff and traffic officers who deal with the aftermath of accidents
Driving test centre strikes
- Some driving examiners are on strike in the East Midlands, West Midlands, east of England and parts of London
- The industrial action will not affect theory tests but might have an impact on practical exams
WED 4 JAN
Rail disruption continues
- The National Union of Rail, Maritime and Transport Workers (RMT) are on strike
- The RMT strike will affect services in England, Scotland and Wales and people are being advised to avoid travelling if possible
Read more: What are the train strikes about?
Bus drivers on strike
- Bus drivers in London are taking industrial action
- The routes affected are mostly in south and west London
Possible road disruption
- Some National Highways traffic officers across England are on strike
- The strike involves control centre staff and traffic officers who deal with the aftermath of accidents
Driving test centre strikes
- Some driving examiners are on strike in London, south-east and south-west England and Wales
- The industrial action will not affect theory tests but might have an impact on practical exams
THU 5 JAN
Rail disruption continues
- Train drivers across 15 rail companies represented by the Aslef union are on strike
- The rail companies affected are: Avanti West Coast, Chiltern Railways, CrossCountry, East Midlands Railway, Great Western Railway, Greater Anglia, Great Northern/Thameslink, London North Eastern Railway, Northern Trains, Southeastern, Southern/Gatwick Express, South Western Railway, SWR Island Line, TransPennine Express and West Midlands Trains
- Passengers are advised to check the availability of services before they travel
Read more: What are the train strikes about?
Bus drivers on strike
- Bus drivers in London are taking industrial action
- The routes affected are mostly in south and west London
Driving test centre strikes
- Some driving examiners are on strike in London, south-east and south-west England and Wales
- The industrial action will not affect theory tests but might have an impact on practical exams
FRI 6 JAN
Rail disruption continues
- The National Union of Rail, Maritime and Transport Workers (RMT) are on strike
- The RMT strike will affect services in England, Scotland and Wales and people are being advised to avoid travelling if possible
Read more: What are the train strikes about?
Possible road disruption
- Some National Highways traffic officers are on strike in the East Midlands and eastern England
- The strike involves control centre staff and traffic officers who deal with the aftermath of accidents
Driving test centre strikes
- Some driving examiners are on strike in London, south-east and south-west England and Wales
- The industrial action will not affect theory tests but might have an impact on practical exams
SAT 7 JAN
Rail disruption continues
- The National Union of Rail, Maritime and Transport Workers (RMT) are on strike
- The RMT strike will affect services in England, Scotland and Wales and people are being advised to avoid travelling if possible
Read more: What are the train strikes about?
Possible road disruption
- Some National Highways traffic officers are on strike in the East Midlands and eastern England
- The strike involves control centre staff and traffic officers who deal with the aftermath of accidents
Driving test centre strikes
- Some driving examiners are on strike in London, south-east and south-west England and Wales
- The industrial action will not affect theory tests but might have an impact on practical exams
SUN 8 JAN
Driving test centre strikes
- Some driving examiners are on strike in London, south-east and south-west England and Wales
- The industrial action will not affect theory tests but might have an impact on practical exams
MON 9 JAN
Driving test centre strikes
- Some driving examiners are on strike in London, south-east and south-west England and Wales
- The industrial action will not affect theory tests but might have an impact on practical exams
TUE 10 JAN
Bus drivers on strike
- Bus drivers in London are taking industrial action
- The routes affected are mostly in south and west London
Teachers in Scotland
- Some primary school teachers in Scotland are on strike
- Members of the NASUWT union are taking action as part of an ongoing dispute over pay
Read more: Which schools will teachers' strikes affect?
Driving test centre strikes
- Some driving examiners are on strike in London, south-east and south-west England and Wales
- The industrial action will not affect theory tests but might have an impact on practical exams
WED 11 JAN
Ambulance staff on strike
- Ambulance staff in London, Yorkshire, the North West, North East and South West of England are on strike
- The strike affects non-life threatening calls only and people are advised to use the 999 service in an emergency
Read more: Why are ambulance staff striking?
Teachers in Scotland
- Some secondary school teachers in Scotland are on strike
- Members of the NASUWT union are taking action as part of an ongoing dispute over pay
Read more: Which schools will teachers' strikes affect?
THU 12 JAN
Bus drivers on strike
- Bus drivers in London are taking industrial action
- The routes affected are mostly in south and west London
FRI 13 JAN
There are currently no national strikes planned for this date
SAT 14 JAN
There are currently no national strikes planned for this date
SUN 15 JAN
There are currently no national strikes planned for this date
MON 16 JAN
Bus drivers on strike
- Bus drivers in London are taking industrial action
- The routes affected are mostly in south and west London
Teachers in Scotland
- Teachers in Glasgow and East Lothian are on strike
- Members of the Educational Institute of Scotland (EIS) are taking action as part of an ongoing dispute over pay
Read more: Which schools will teachers' strikes affect?
TUE 17 JAN
Teachers in Scotland
- Teachers in Perth and Kinross and North Ayrshire are on strike
- Members of the Educational Institute of Scotland (EIS) are taking action as part of an ongoing dispute over pay
Read more: Which schools will teachers' strikes affect?
WED 18 JAN
Nurses in England on strike
- Members of the Royal College of Nursing (RCN) are taking industrial action over pay
- Life-preserving treatment must be provided, and all nurses in intensive and emergency care are expected to work
Teachers in Scotland
- Teachers in Orkney and Fife are on strike
- Members of the Educational Institute of Scotland (EIS) are taking action as part of an ongoing dispute over pay
Read more: Which schools will teachers' strikes affect?
THU 19 JAN
Nurses in England on strike
- Members of the Royal College of Nursing (RCN) are taking industrial action over pay
- Life-preserving treatment must be provided, and all nurses in intensive and emergency care are expected to work
Bus drivers on strike
- Bus drivers in London are taking industrial action
- The routes affected are mostly in south and west London
Teachers in Scotland
- Teachers in Moray and North Lanarkshire are on strike
- Members of the Educational Institute of Scotland (EIS) are taking action as part of an ongoing dispute over pay
Read more: Which schools will teachers' strikes affect?
FRI 20 JAN
Teachers in Scotland
- Teachers in Angus and East Dunbartonshire are on strike
- Members of the Educational Institute of Scotland (EIS) are taking action as part of an ongoing dispute over pay
Read more: Which schools will teachers' strikes affect?
SAT 21 JAN
There are currently no national strikes planned for this date
SUN 22 JAN
There are currently no national strikes planned for this date
Teachers in Scotland
Almost all secondary schools across Scotland will be closed on Wednesday as teachers continue their action in a dispute over pay.
It is the second day of action after primary schools were closed all day on Tuesday.
Last-ditch talks between unions and Scottish government officials held on Monday failed to prevent walkouts.
The strikes involve members of the EIS, NASUWT, Scottish Secondary Teachers' Association (SSTA) and the Association of Headteachers and Deputies (AHDS) unions.
They have rejected a 5% pay increase, arguing for 10%. The latest offer includes rises of up to 6.85% for the lowest-paid staff.
If no agreement is reached, teachers in Scotland plan to strike on a further 16 days, beginning next week.
The days of action - split across every council in Scotland - will take place throughout January and into February.
How are you affected by the strikes? Are you taking part in strike action? You can email: haveyoursay@bbc.co.uk.
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