More than 70 per cent of those who took part in the ballot on Friday and Saturday voted against a 14.3 per cent pay rise.
It means that more than 3,100 members of the Unite union will now walk out next week, meaning 93 per cent of the bus network across the Black Country and wider West Midlands will be hit.
National Express West Midlands has said there will be a limited service serving the West Midlands' major hospitals during the strike action.
Union bosses have accused National Express of being an "extremely wealthy company and makes considerable profits from the hard work of our members, who are not paid enough for the difficult and stressful job they do".
In response, bosses at the bus company have said they have "made an offer, which we believe is fair and responsible".
Here's the information you need to know ahead of the strike action.
Why are drivers striking?
The row is over pay.
Unite leaders say drivers are not paid enough, something that has been made worse by the current cost of living crisis.
Those at the union say the bus company has not made an acceptable offer.
Although drivers will continue with their strike action, on Friday evening National Express bosses said engineers had voted to accept the new offer of a 14.3 per cent base pay increase along with another 3.5 per cent rise next year. In 2024, should the consumer price index (CPI) reach four per cent or above in December 2023 the company will reopen negotiations with unions.
How long is the strike?
This strike action is indefinite, so it will continue until the situation is resolved.
On its website, National Express said it had "not been advised how long" the strike will last.
Which National Express buses are running?
In a statement, National Express West Midlands said: "A limited service, primarily serving the region’s major hospitals, will operate from Monday. Please do not travel on a National Express bus unless absolutely necessary."
Bosses at National Express West Midlands have said that only the following routes will be running while drivers are striking:
4 Birmingham - Solihull (via Sparkbrook, Tyseley, Acocks Green & Olton)
5 West Bromwich - Sutton Coldfield (via Great Barr, Kingstanding & New Oscott)
6 Birmingham - Solihull (via Sparkbrook, Sparkhill, Hall Green & Shirley)
6 Dudley - Stourbridge (via Russells Hall Hospital, Brierley Hill & Amblecote)
28 Heartlands Hospital - Great Barr (via Ward End, Castle Bromwich, Erdington, Old Oscott & Perry Beeches)
51 Birmingham - Walsall (via Great Barr & Perry Barr)
59 Wolverhampton - Ashmore Park (via New Cross Hospital & Wednesfield)
87 Birmingham - Dudley (via City Hospital, Smethwick, Oldbury & Tividale)
97 Birmingham - Chelmsley Wood (via Bordesley Green, Heartlands Hospital & Meadway)
529 Wolverhampton - Walsall (via Willenhall)
X4 Birmingham - Falcon Lodge (via Aston Expressway, Erdington, Sutton Coldfield & Good Hope Hospital)
X21| Birmingham - Bartley Green (via Birmingham University, Selly Oak & Weoley Castle)
Temporary timetables for these routes are on the National Express West Midlands website.
National Express has also said it expects services to be busy, and as the week goes on bosses hope to add back in more services.
There will also be no school services.
What about other bus operators?
The strike only affects National Express West Midlands services.
Other operators, such as Diamond Bus, are set to be running their routes as usual.
In a statement, Diamond Bus its services will "not be affected by the strike action and will continue to operate as normal".
A spokesperson added: "For those National Express customers who will be affected by service disruption, Diamond provides a wide variety of regular bus services across the West Midlands, and we advise you to check our website for alternative services that may enable you to continue to your travel requirements and complete your essential journeys."
Can I use my National Express ticket with another operator?
No, passengers will have to buy tickets from other operators.
Diamond Bus has said it does not accept National Express tickets on its services.
The same also applies to the West Midlands Metro tram service.
⚠️NX West Midlands Bus Strikes ⚠️— West Midlands Metro (@WMmetro) March 19, 2023
The NX Bus Strike Action will be going ahead on March 20 onward until further notice. There will be NO TICKET acceptance in place on our services. We are also asking our customers NOT to purchase the Metro+NX Bus Tickets for travel from March 20 pic.twitter.com/E2aFBKkRZX
Can I get a refund?
From Monday, National Express West Midlands customers can fill out a refund form which will appear on the dedicated page about strike action on the bus operator's website.
In a statement, the company said: "A pro-rata refund will be issued for days affected by the strike action. The refund will be calculated on ticket type, usage and duration of the strike action.
"If you are entitled to a refund it will get processed when your ticket expires or the strike concludes (whichever is first). Once our team has processed your refund the bank will then need to transfer the funds to your account; this part of the process could take up to five working days. Please do not contact us after you have filled in the form.
"National Express can only refund for the days you were unable to travel during the strike period back to the original method of purchase."
The bus operator has said it will not implement a processing fee on refunds.
National Express will not pay additional costs incurred by customers who have had to find other ways to travel to medical appointments, work or school.
Schools and colleges
Dudley College of Technology has said classes will take place as normal during the strike.
However, for transport to lessons, chief executive and principal Neil Thomas said: "Any student in receipt of a college National Express only bus pass who has to pay for a ticket on an alternative bus provider (such as Diamond) will have this expense reimbursed by the college. Students need to present their ticket to receive a cash refund.
"Details of the locations where tickets can be presented will be shared shortly. Students already in receipt of a multi-provider bus pass will be able to use any of these alternative routes using the existing pass."
He added: "If students have no alternative travel options available to them, we will be supporting with online access to classroom sessions. These should only be used by exception where travel is impossible. Your tutor will provide details on how to access online lessons and resources."
City of Wolverhampton College has told students: "Classes will continue as normal, but we are understanding of the disruption this may cause you. Please consider your journey in advance and discuss with your tutors how this may affect your attendance."