Bus advertising is used by media buyers to advertise out-of-home. This form of advertising is beneficial because you can customise your campaign and, control the location of delivery. Other benefits include:

Impact

Bus advertisements are unavoidable because they immediately catch the public eye. They are successful at building immediate brand awareness and delivering product offerings. Striking and remarkable advertisements are likely to have a substantial impact on your company. 

Frequency

Bus advertising is an easy way to keep your Brand or ad fresh in consumers’ minds. The constant reminder on the same routine bus route creates a repetitive image, which can lead to a higher chance of purchase. 

Advertisers can place their campaigns on routes that are most applicable to their chosen target market. Bus ads can be viewed by customers at any point throughout the day, while they are on the go. It is the perfect means to advertise to a targeted demographic with this Moving Billboard.

Low Cost

Finally, bus advertising is relatively cheap compared to other media platforms. Out-Of-Home advertising has one of the lowest CPM in the industry (read more about it here), outperforming more common advertising tactics.

Source: https://blog.allovermedia.com/blog/5-awesome-advantages-of-transit-advertising