Speed (traffic planning)
In traffic planning , different speeds are decisive for the design of road traffic systems . They are used as guide values and serve either as a specification for the dimensioning or as a specification for the speed actually driven during operation.
Design speed v e
The design speed v e is a guideline value in the design of traffic routes , which is determined for the structural dimensioning of the route. It is a term from the guidelines for the construction of roads , part: Lines ( RAS-L ). v e depends on the desired network function of the road and the desired quality of the traffic flow and should, if possible, remain constant over longer distances. The network function in turn is determined by the RAS-N , the desired quality depends on the desired security and economic efficiency.
Influence of v e
The design speed influences a number of parameters of the design planning. These include:
- Minimum curve radius
- Clothoid parameters
- Maximum length of straight lines
- Maximum pitch
- Tip and tub minimum radius
- Bank
Speed v 85
In contrast to this, the speed v 85 represents a control variable with which the dynamic driving dimensioning of the location and height plan as well as the cross-section is checked. It should reflect the actual driving behavior and describe the speed that is not exceeded by "85% of the unhindered driving cars on a wet road". The v 85 varies depending on the nature of the route , which is also permitted within certain limits. A number of design elements are also determined with the speed v 85 (e.g .: transverse slope in the curve, required stopping visual range , necessary overtaking visual range and minimum radii for a negative transverse slope).
In order to coordinate the route characteristics and the driving behavior of the vehicle driver with one another, it is necessary that v e and v 85 are in a balanced relationship. Differences of more than 20 km / h should be avoided.
The speed v 85 is usually determined via speed measurements when the deviation of the actual maximum speed driven from the maximum permissible speed is significantly too great.
Project planning speed v P
The project planning speed is a planning variable that is used in Austria and Switzerland. It represents the highest theoretical speed with which a road can be driven at one point with sufficient safety. With the help of the project planning speed, among other things, the minimum values of the visibility and the required cross slope are determined.
Rated speed v B
| Standard cross-section | Rated speed (in km / h) |
|---|---|
| RQ 35.5 / RQ 29.5 | 110 to 80 (70) |
| RQ 33 / RQ 26 | 100 to 70 (60) |
| RQ 26 / RQ 15.5 | 90 to 60 (50) |
| RQ 10.5 | 80 to 50 (40) |
| RQ 9.5 | 60 to 50 (40) |
As a specification of the road network planning , the traffic quality of a route section can be verified with the aid of the rated speed v B. It is to be regarded as the planned mean value of the travel speed of all cars for a road to be measured.
Depending on the standard cross-section , the adjacent rated speeds are to be selected for roads without cultivation (values in brackets apply to difficult terrain):
Node speed v k
The intersection speed represents the speed that is assigned at a intersection of the continuous, higher-level road. Important construction elements of a node are dimensioned with the help of the node speed. For example, the warping length of widenings or the delay distance of turning lanes depend on the speed of the intersection.
Instantaneous speed
The instantaneous speed reflects the speed of a vehicle at a certain road cross-section at a certain point in time. A distinction must be made between local and instantaneous speed. The local speed v l forms a sequence of instantaneous speeds in relation to the cross section. In contrast, the instantaneous speed v m represents a sequence of instantaneous speeds that is related to the point in time.
Freehand speed
The free-hand speed is the vehicle speed in a curve at which the centrifugal force and gravity acting on the vehicle are in equilibrium when the road is banked. The vehicle does not change course at this speed and can be driven "hands-free".
Steady-state speed
The steady-state speed describes the speed of a vehicle, which is reached with a balance of tractive effort and driving resistance.
See also
Web links
- Information on the design and dimensioning of roads ( Memento from August 11, 2014 in the Internet Archive ) (PDF; 570 kB)
- Explanation of terms traffic counting characteristic value (PDF; 92 kB)
Individual evidence
- ^ Natzschka: Road construction, design and construction technology . BG Teubner Verlag, 1996, ISBN 3-519-05256-3
- ^ Pietzsch, Neuwied: Street planning . 7th edition. Werner Engineer Texts, 2004, ISBN 3-8041-5003-9
- ↑ SN 640 080b - Project planning, basics - Speed as a project planning element. ( Page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. (PDF; 470 kB)
- ↑ Frank Höfler: Transport Practice - Volume 2: Transport Technology . Bauwerk-Verlag, 2006, ISBN 3-934369-53-7 , p. 48 ff.
