Selling more ads would probably increase revenue for the metro systems. Making them bigger and selling them for more would help as well. Google doesn't apply he

Selling more ads would probably increase revenue for the metro systems. Making them bigger and selling them for more would help as well. Google doesn't apply here because they can't use this technique for fear of backlash. I can't imagine anyone complaining about more/bigger ads on buses, especially if it helps reduce subsidies and spending.