Article 158 of the Burundi Highway Code splits the public passenger transport licence into D1 and D2. What distinguishes them?

1. D1 covers public transport vehicles of between 9 and 30 seats; D2 covers those with more than 30 seats
2. D1 covers diesel buses and D2 covers petrol buses
3. D1 is for urban routes only and D2 is for interurban routes only
4. D1 is a provisional licence and D2 is the definitive version of the same licence