"km emissions" refers to the amount of harmful gases or pollutants released into the atmosphere by a vehicle for every kilometer it travels. It is a measure of the environmental impact of the vehicle's exhaust emissions. Full definition
The D3 isn't quite so impressive, as its 114g / km emissions rating means an 18 per cent BIK rating and a little road tax each year (only # 30 admittedly). (evo.co.uk)
That 41g / km emissions figure compares favourably with the Audi A3 e-tron (38g / km) and family friendly VW Passat GTE (39g / km), but isn't quite a match for the Prius Plug - in (22g / km) or BMW i3 (12g / km). (autoexpress.co.uk)
It returns 35.8 mpg on the combined cycle, while 183g / km emissions mean # 200 - a-year road tax. (autoexpress.co.uk)