The house edge at roulette (with single zero) is familiar to most players,
it is 1/37th or in other words 2.70% of the volume.
For easy chances (like red) it depends on the Zero-payout-scheme, but mostly it is the half, e.g. 1.35%.
Some online or slot players do not know the "second tax"
of the European roulette, called the Tronc.
Depending on the country, or even the casino table the rules for Tronc are different,
generally it can be said:
The Tronc costs 1 piece of the profit of a single Number.
Traditionally, then after a win at the casino it sounds like: "one piece for the employees".
Thus, the house edge is already 2/37th of or 5.40%.
This post will now be less about the Tronc itself,
as the precise description of the specific casinos can be found in brochures or on their websites.
Betting only one number, you just can not avoid the Tronc.
But as soon as more numbers than one Single are bet, you can bypass the Single-tax sometimes.
Lying namely two of the set Singles on the tableau (the game table) side by side,
so you can bet them as a Split.
Free singles from tronc
The more Single numbers that are played, the better the chances of avoiding the Tronc.
Ideally, one should combine as a much lower chances as possible, this can free singles from tronc.
So would e.g. the numbers from 1 to 12 be the first dozen, or all red Singles the easy chance Red.
This method not only saves you the Tronc, the bet itself gets easier as there are fewer chips to set.
This chart is good to see to what extent of Single-bets can be replaced with lower chances: 
The horizontal axis shows the number of the original Single bet.
On the vertical axis the number of chances that could replace this Singles is shown.
For the graph 20000 random number combinations were used between 1 and 36 single numbers.
The color represents the number of such combinations according to the scale.
Since the numbers of ECs Odd / Even and Black / Red for a summary of chances
is distributed unfavorably on the table, arises at the right edge of the graph an "island".
It is the consequence of this irregularity.
For example 20 Singles, would be replaced with about 10 chances (in median) which contain these Singles.
An example for the conversion of 27 Singles. In the graph above, this constellation would be to found 27 right and 10 high.
27 Singles: 0 3 5 6 7 8 9 10 11 12 14 16 17 20 21 22 24 26 27 29 30 31 32 33 34 35 36
replaced with:
1 TVS 7 /12 7 8 9 10 11 12
2 TVS 31/36 31 32 33 34 35 36
3 Corner 26/30 26 27 29 30
4 Split 0 / 3 0 3
5 Split 5 / 6 5 6
6 Split 14/17 14 17
7 Split 20/21 20 21
8 N 16 16
9 N 22 22
10 N 24 24
If you want to implement this approach in the real game, it's very quickly clear:
This is not so trivial.
Therefore, the roulette strategy simulator does this for you automatically, if optimize chances is used.
The advantage for the own strategy can be determined with a few mouse clicks:
Just run a test with and without this function on the same permanence (number list).
In practical terms, you can use this function via Live-Mode.
Have fun with roulette strategies,
trizero
