You need to put a potetiometer in place of your resistor to be able to make the speed ajustment. You should use at least a 1M, I think.
There are two different traffic light examples available, look in the sample circuit "blue folder icon" in the Educational version of Multisim that implements a traffic light:
The first choice uses programmable ladder logic with an actual traffic light simulation. For choice two, you can export the sample to program the NI Digital Electronics FPGA Board.
Drag n drop these snippets directly into your Multisim workspace 🙂
*I also attached a short version of the NI Multisim for Education PDF specifically for traffic light designs.
Find the attached files below. Hope this helps!