Addition of critical vehicle power loads

The addition of critical current load vehicle ( AKF ) said method is a method of approximate calculation of signal schedules of light signal systems .

basis

Axel W. Gleue introduced the process to the transport science community in his dissertation in 1972 .

The basic idea of the method is that a traffic light system to the maximum traffic volume is to be interpreted that not without conflict about the intersection can drive. For this purpose, the maximum sum of the traffic volume is selected from all incompatible combinations of vehicle flows . The required release time and the resulting cycle time can be calculated from this. For the sake of simplicity, it is assumed that the mutually incompatible currents of maximum strength pass the intersection in blocks one after the other .

Determination of the relevant traffic flow rate

1. All currents that can flow freely (e.g. green arrow control) or do not occur are rated with 0.
2. For lanes that are used in different directions, the total load is entered.
3. If there are several lanes in each direction, the maximum load is entered.
4. If several currents have to be released at the same time, the maximum load in each case must also be taken.
5. The values ​​obtained in this way are entered in columns in which there are incompatible currents among each other.
6. Form the column sums.
7. The maximum of the column sums is the decisive traffic flow rate.

Determination of the cycle time of the traffic light system

The orbital period of the traffic signal is composed of release times and lost time . The release time must be calculated for the relevant traffic flow and the saturation flow . ${\displaystyle t_{\text{uml}}}$ ${\displaystyle t_{\text{frei}}}$ ${\displaystyle t_{\text{ver}}}$ ${\displaystyle q_{\text{massg}}}$ ${\displaystyle q_{\text{sät}}}$

The formula here is ${\displaystyle t_{\text{uml}}={\frac {\sum t_{\text{ver}}}{1-{\frac {\sum q_{\text{massg}}}{q_{\text{sät}}}}}}}$

rating

The method uses a simplified assumption of the processes in a traffic light system. Thus, foot traffic , bicycle traffic and special public transport phases ignored. Many estimated values ​​are also included in the calculation. For these reasons, better methods must be used to more accurately calculate the signal schedule. However, the AKF method is used to roughly estimate the cycle time and can therefore serve as an initial decision-making aid.

example

The following simplified intersection without a turn is given:

• 

We now consider stream A. This cannot be released at the same time as stream D, for example. These are therefore critical to each other :

• 

If we now want to add the current C, it is no longer critical . Current D and C can operate at the same time, so only the larger current D is decisive for the dimensioning:

• 

If you now calculate all currents together you get the following matrix:

${\displaystyle {\begin{matrix}{\text{kritische Str}}{\mbox{ö}}{\text{me}}&{\text{A+C}}&{\text{A+D}}&{\text{B+C}}&{\text{B+D}}\\A&100&100&\\B&&&200&200\\C&50&&50&\\D&&150&&150\\\sum &150&250&250&350\end{matrix}}}$

The most critical vehicle flows here is therefore the combination of B and D. The intersection must be designed for these 350 vehicles. The currents A and C are of minor importance and can flow off from B and D during the green phases.

See also

• Traffic light guidelines
• Signal schedule
• Release time
• Addition time
• Meanwhile
• Signal location plan

Individual evidence

1. ↑ Axel W. Gleue: "A contribution to the simplification of the calculation process for signal programs", Darmstadt, 1972
2. ↑ Dietmar Bosserhoff: "Junctions with traffic lights" p. 22f ( Memento from September 8, 2012 in the Internet Archive ) (PDF file; 4.53 MB)
3. ↑ P. Ebert: “Spatial and Infrastructure Planning, Collection of Formulas for Transport” p. 8f  ( page no longer available , search in web archives ) (PDF file; 187 kB)
4. ↑ Dietmar Bosserhoff: "Junctions with traffic lights" p. 25 ( Memento from September 8, 2012 in the Internet Archive ) (PDF file; 4.53 MB)
5. ↑ Dietmar Bosserhoff: "Junctions with traffic lights" p. 27 ( Memento from September 8, 2012 in the Internet Archive ) (PDF file; 4.53 MB)