# Short Cyclic Algorithm for Turbo Block Construction
## 7 Discussion and Conclusions  
This paper presents both a new methodology and algorithmic solution for the design of a turbo block.  
There are four main characteristics that make this methodology different from those present in relevant national policies:  
* This method relies on the fixed width of the first segment and changeable width of the last segment of the spiraling lane. There are two reasons for this. The first reason is that the critical vehicle negotiating the first segment travels along the minimal radii and, after entering the segment, shifts from maximum right to maximum left off-tracking, making the trajectory the list predictable just in this part of the spiraling lane. The second reason is the fact that, if the last segment of the spiraling lane is kept at a constant width and if the width of the last segment is sufficient at its start, there would be surplus pavement along the entire length of the last segment.
* The method presented herein supports both matching the curb lines or marking lines between the consecutive segments. The problem of matching either the marking or curb lines arises when the innermost and outermost edge lanes are wider than those along the dividers. In some national policies, there are discontinuities (jumps or gaps) at the transitions between the segments, while in some other policies, the problem is not sufficiently elaborated. In the methodology presented herein, there are two strictly delineated construction techniques--one based on matching the curb lines and another one matching the marking lines. Both construction techniques were resolved and supported.
* In many national policies, not all the centers of spiraling lanes are strictly defined. Even in Dutch policies, center positions are not defined in numerical terms, i.e., by using differences between the radii or some other simple parameters. In this methodology, each center of every segment is precisely positioned, by using simple parameters, such as radii, differences between radii, and the angles of translation axes.
* Finally, all the parameters discussed above were put into a compact cyclic algorithm that can be easily translated into programing code. An example in AutoLISP is given as it is the most suitable environment for geometrical calculations and produces very quick graphical results.  
As for the algorithm (program) itself, it may be too compact for more advanced deployment. The design process of a turbo roundabout does not end with the turbo block construction and roundabout legs have to be added in the next step. Automated addition of roundabout legs would require additional attributing of the turbo block arcs. These attributes would help entry and exit lanes of the legs to automatically find their correspondent spiraling lanes, thus enabling automatic construction of the turning geometry. Such an addition does not complicate the algorithm itself and just introduces attachment of some non-numerical data to the arcs. The technology in question has already been developed, but algorithmic construction of turbo roundabout legs is too large to be published in a scientific paper.  
As for the methodological aspect of this paper, detailed analysis of the trajectory in the first segment of the spiraling lane is planned in the near future. It is expected that the width of the first segment would be increased in a relation to the most relevant national polices of the world.  
Conceptualization, S.V. and D.G.; methodology, S.V. and D.G.; software, D.G. and S.V.; investigation, S.V., S.F., V.I. and F.T.; supervision, D.G., V.I. and S.F.; visualization, S.V., F.T., M.L. and N.M.; writing--original draft preparation, S.V. and D.G.; writing--review and editing, S.V., D.G., S.F. and V.I. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The data presented in this study are available in the article.  
The authors declare no conflicts of interest.