For 'qualifying aircraft' .. (eg, jet, multicrew, trubo-prop with autofeather etc), IFR take-off minima is 550 meters vis and 0 ceiling but in the event of an engine failure and you can't return to the departure aerodrome to land because it's below approach and landing minima, then you need to assure that your aircraft has the performance to meet terrain clearances and the fuel to proceed to a suitable airfield. You need high intensity runway lights and runway centerline lights for this, otherwise it's 800 meters vis and 0 ceiling.
In the US, we can take off with an RVR of 600 feet (182 meters), but need RVR reports at threshold, midfield, and end of the runway, and the runway centerline and edge lighting as well.