Ventana software support forum

Might be an easy question, but since I am a beginner with vensim I have the following question:
How do I build a formula that is an under-capacity-threshold. EG: The subject is about road lanes and construction. How do I make a formula that states. If the needed capacity is 1.5 times higher than the actual capacity for a period longer than 3 years new lanes will be constructed. So only if Variable A is higher then Variable B for a period of multiple time steps. A certain value is changed. Can someone please tell me which Vensim Formula to use?

thanks in advance,

A Vensim Beginner

There is no formula to calculate this.

Start by calculating the number of days the needed capacity is over 1.5 * actual capacity (use a level, maybe call it "time over capacity"). If it's lower, reset the level (you can find out how to do this on the forum). When the level "time over capacity" reaches 3 years, start construction.