Adapt average speed for group rides

Just have come back from a trip with friends to France and Switzerland.
Planning nice curvy roads with MRA for 11 routes was fun.
But:
the calculated times for viapoints most of the time were too optimistic for our group (cruisers).
Of course, as this will depend on type of bikes and experience of the drivers in a group I propose a simple solution:Add to Toolkit a new function.
"Adapt average speed (for group rides)"
Then e.g. on a slider one can choose a "correction factor" e.g. from 20% ... +10% (for fast bikes)
You could use this factor then on all types of roads for calculating of the estimated times.So it is then up to the excperience of the tourguide to set the factor appropriately.

@Klausr fun idea!

@CorjanMeijerink Maybe "Adapt average speed" is misleading.
One could implement it vice versa.
"Adapt time calculation (for groups)"
= "Zeitberechnung (fΓΌr Gruppen) anpassen"
+10% ... 20%
where +10% means group drives faster than normal, results in shorter time intervalls,
and 20% means group drives slower, longer time intervalls. 
@Klausr
or
10% = reduce ETA by 10%
+20% = extend / prolong ETA by 20% 
@Klausr I definitely support this request, but I would suggest to keep the adjustment to affect the speed. Time is relative for type of roads that are picked out. For me personally when we ride a 60km/u road, we on average take it at approx 70 to 80km/u. So the control should simply increase the speed limit per road. The algorithm itself will then account for the shorter ETA.

@StefanHummelink Is this you on the speed camera

@StefanHummelink
Well, I think this depends on how the algorithm to find the fastest road between 2 waypoints and the time calculation is implemented in MRA.In a former gps I used, there was an ini file with a speed profile for each vehicle type with speeds for e.g.
interstate
highway
major road
minor road
local roadI manipulated these values to get results which fit better to my driving style.
But I wanted to propose a simple solution:
to apply a correction factor to all of these type of roads.
So, if you drive faster simply add x% to these speed values, or multiply by 1,x.
If you drive slower than substract x%, or multiply by (10,x)Of course, there may be better solutions but I thought KISS
Keep it Small and Simple 
@NickCarthew No license plate captures. I see no issue at all muhahahaha!

@Klausr that is exactly what I would like as well. i.e. the option to correct all speed limits by 20%.
That means 36km/u in 30km/u zone, 60km/u in 50km/u, 72Km/u in 60 and 96km/u in 80km/u.
The numbers above suit me and my group very well.
What I wanted to say is that I prefer the correction on speed which results in a correction on time, rather than a quick and dirty correction in Time for the grand total. 
@StefanHummelink Well, in my group of cruisers with choppers it is quite the opposite.
On a road e.g. with limit 100km/h they drive 8590km/h which means we will arrive later than estimated
(and which makes me crazy sometimes...)
which means the speed of that road should be reduced for calculation.I am curious to see which solution MRA will offer.

@Klausr So 10% for you, +10% for me. A simple list of percentages would suffice!

@StefanHummelink

So, one can name the new function
Adjust speed = Geschwindigkeit anpassenMight also be useful for MRA users with other type of vehicles like cabriolets, oldtimers etc.