You're probably not doing it right (sorry). As you start to expand, you need to look at your set up critically, and start moving your resources around.
For instance, if you start building a city and have 30 stations within a tight cluster, you might have 10 HAZMAT units across them.
Then, you expand out into "the country" and build another 10 stations, but across the same geographical area.
Logically, you now need to move half your HAZMAT units out to these new stations, to have the same coverage (or alternatively, build 10 new HAZMAT units)
I like to play IRL ("in real life") - but there is a limit to that. I built the real-life units at the real-life stations, but then add new units where required.
The heatmap in LSSM is brilliant for this!
EDIT: changed typo of "unit" to "station"