I just added another text field for you to change reaction time.

If you click the link VIEW (just below the simulation). Another web page will show up. And you will find an interface similar to EJS (the tool I used to create the simulation).
In the Model -> Variable tab: You will find all the variables defined in EJS.
For example: reaction time is defined in view sub-tab. the initial value is 0.5 (unit s).

What I just did was add another html command:

reaction time=<input type=text name=reactionTime value="0.5" onChange="document.trafficcontrol._model.reactionTime=parseFloat(this.value);" size=3>s