In the bottom left-hand corner of the webpage, where it indicates different modes of transport, just tick the box next to the reefer icon and it'll calculate the extra time required for those that are stoned.

Or click on the beer glass icon and it'll do the same calculation for pissed travellers.

Should you be under the influence of both, just tick both boxes and it'll give you a combined total of the extra time required to complete your journey.

Enjoy your journey, sir!