Depending on pollutant emissions generated by the motorcycle corresponding one of the four types different classifications of environmental labels:

• Zero: electric motorcycles with more than autonomy 40 km.
• Eco: electric motorcycles with less autonomy 40 km.
• C: Motorcycles homologated under the Euro standards 4 and Euro 3.
• B: Motorcycles homologated under the Euro standard 2.

Source and image: http://revista.dgt.es/es/noticias/nacional/2018/04ABRIL/0404Etiquetas-ambientales-para-motos.shtml#.XN0eTY4zaUk