The Swiss Association of Engineers and Architects (SIA) decided not to revise its recommendation SIA 172 "Construction of rural roads", but to hand the subject over to the VSS for revision and publication in their collection of standards. By this decision the VSS collection of standards is extended to the secondary traffic surfaces, which has hardly been treated until now.
The applying research institution developed two standards, which regulate the bases, the criteria of use, choice, execution and maintenance of pavements in unbound construction with and without overgrowth, in collaboration with the VSS Expert Commission 6.01 "Maintenance". During these discussions it became obvious, that the whole subject of secondary traffic surfaces (roads, paths and squares) should be treated in a group of standards together with the aspects of design.
These standards concern horizontal and vertical alignment, cross fall, drainage installations as well as the strong relations between construction, maintenance and operation. According to the Commission the subject should be treated in two separate standards for rural roads and car parks.
The research work contains the execution of the necessary research in situ and in literature, developing the standards "Design of rural roads" and "Design of car parks" in collaboration with the Expert Commission 6.01 as well as writing the research report.
The information gathering mainly includes research in the literature, surveys of road administrations, in project planning engineers and exporting business owners about their experiences and the use of results from past field tests.
The research provides the fundamentals of project planning of freight roads and parking lots, especially with superstructures in unbound construction. It contains proposals for the two standards "Design of rural roads" and "Designing of parking" and a research report with the results of the information gathering and a commentary on the standards.
Following conclusions we can found in the research report:
1. Design of roads with low traffic density
- choice of type of pavement and design thickness of conventional roads are mainly dependant of traffic
- the decision must be first made as to wether flexible or rigid construction is suitable
- the simple and practical criteria of choice and basic norms for design thickness were produced in the norm.
2. Design of car parks
- the choice of drainage system must be based on the guide (there exists a diagram to simplify the procedure)
- in the matter of seepage, aspects of the retention of surface water and the necessity of having a fall on overgrown flexible pavements were investigated
- every variation of cross sections, as well as the execution of seepage areas, run-offs and gutters is well documented