Is it permissible to work as a bus driver of a bus carrying advertisements for haraam things?

Praise be to Allah.

We praise Allah, may He be exalted, for having guided you to Islam and we ask Him, may He be glorified and exalted, to make you steadfast in Islam and to increase you in guidance. 

We appreciate your concern about what is halaal and asking about the ruling on your work, and we ask Allah to make good easy for you and to reward you, and to help you to avoid evil and sin. 

With regard to your job, what appears to be the case is that it is not permissible to work as the driver of a bus that carries adverts on its side for sinful matters that incur punishment, such as ads for alcohol and immoral activities. Working as a driver is not separate from those advertisements that are on the bus he is driving. Based on that, it may truly be said concerning his job that it is helping to promote those immoral actions and haraam things, so this is helping in sin which Allah, may He be exalted, has forbidden in the verse (interpretation of the meaning):

“Help you one another in Al‑Birr and At‑Taqwa (virtue, righteousness and piety); but do not help one another in sin and transgression. And fear Allaah. Verily, Allaah is Severe in punishment”

[al-Maa’idah 5:2]. 

You should understand that Allah, may He be exalted, has not restricted halaal means of earning a living and permissible work. And you should also understand that whoever gives up something for the sake of Allah, Allah will compensate him with something better than it. Allah, may He be exalted, says (interpretation of the meaning):

“And whosoever fears Allaah and keeps his duty to Him, He will make a way for him to get out (from every difficulty).

3. And He will provide him from (sources) he never could imagine”

[al-Talaaq 65:2-3]. 

We ask Allah to make it easy for you to find a good and blessed halaal source of provision. 

Please see also the answer to question no. 87788 

And Allah knows best.