Fleet numbering logic

All of our buses in OMSI have fleet numbers assignes using following logic:

10xx - small citybus
12xx - standard citybus
15xx - tri-axle citybus
18xx - arcticulated citybus
20xx - arcticulated citybus XL (20m+ or tri-articulated)
22xx - double-decker citybus

Intercity/coaches use same schema but +100 (so standard intercity buses are 13xx and tri-axle 16xx etc)
Wrong side of the road buses use same schema also, but instead have +4000 to their numers (so standard would be 52xx and double decker 62xx)

xx is the first unused number in that available section

And the beginning numbers for main categories from our current system come actually avg length of the buses in that category. 10xx = 10m, 12xx = 12m, 15xx = 15m, 18xx = 18m etc