How to tell when you need more teamsters?

[Killer Tamashi]

I generally have my products somewhere between 1000-200 sitting in my industries/raw resources production buildings and I honestly can't tell if that's just *normal* or if I need more teamsters to move stuff around

[Silent_Shadow]

I would say when the storages of factories are about halfway full is good. If the outputs of various buildings look too full, then you should get more teamsters (or make them and their routes more efficient).

Too many teamsters and they start carrying a small fraction of their capacity, which is wasteful.

[sir_chewie]

No, 200-1K is good. It's when you run out of mats in industrial buildings or storage space overall that you NEED more teamsters. But you already have a big problem if it ever gets that far.
In my experience, the best ratio is between one teamster per 6 raw/indust buildings and one per 10. But that depends on the era, as first era they have less capacity. And Last era, you have huge sprawl, so it takes more time to move around.
In general, just have a series of mini-cities. A residential & amenities district. Nearby the raw resources, and industries that utilize them. With each set-up capped at around 200-300 citizens. That way, the teamsters are mostly working on short runs. From A to B, B to C, C to docks as well as home, hospital, fun, food, etc. Then a short walk back to another shift.

[Duuvian]

I build more teamster offices when I notice full storage. If it's a really desperate teamster situation I'll turn on the alternate building modes that increases hailing capacity at the cost of some loss of hauled load.

When full storage happens it can also be caused by traffic jams rather than lack of teamsters, First check if it's because you have traffic jams, such as one road leading to the only docks. Then you'll want bus stations to reduce traffic and clear the roads for trucks, and new docks to take exports to other directions. The garages are nice until they cause traffic jams. The metro station helps quite a bit too. Alternate roads can help but often it's harder to get them to take the new roads instead of the congested ones that stuff has already been built around, since the alternate road might have to go out of the way a bit by the time congestion is a problem since the island is already somewhat built up by that point. A better idea if space permits is an alternate dock closer than the one with traffic problems, because often that will be a shorter path and AFAIK traffic doesn't consider if a traffic route is congested, and I think can't decide to take a slightly longer route with less traffic. At the least that doesn't seem to be a high priority when choosing routes.

On some maps tunnels can be helpful as well, that means you can run three tunnels off an intersection that go to different locations on the other side of the hill or cliff the tunnels go through. If you use two tunnels instead of three then two of the intersected roads can lead to different places and hopefully spread the traffic out a bit more, though that's tricky if you didn't plan for that from early on. It might also be necessary later to have two of these tunnel intersections to provide a second intersection to spread traffic as the first might become congested if the connected tunnel areas are developed heavily. Putting a dock on the other side can help a bit if the teamsters are hauling exports from there through the tunnels.

You'll want to limit intersections because the roads are all 2 way and connected roads are all stoplight intersections, instead of off ramps and one-way roundabouts. Roundabout attempts don't work well in Tropico as they create more stoplight intersections for each connecting road rather than uninterrupted flow of rightward turns in a right-side traffic system, unless that's in a DLC I don't have or something.

Cities: Skylines has roundabouts and off ramps and one way streets and it gives more control, though that game has a BUNCH of DLC so I don't play it much due to being sort of crippled by not having some of them; Tropico is better in that regard despite also having DLCs.