When you hire a moving firm to move your stuff, are you allowed to ride with them?

I do not know about other moving companies, but Sing Movers, Removalists Melbourne Company move your things and would allow you to go with them.

but only one person is allowed to go with them.

As others have said: no, and only the most fly-by-night outfits would even consider it, commercial carriage of people is a whole regulated thing.

You do have an option: rent a truck and hire a crew or arrange friends yourself. Obviously you can ride in a truck that you rented, you can choose the route and the time, and you have full control over what gets packed. Be prepared to pay extra for damage insurance on the truck, because a driver's normal insurance won't cover a commercial vehicle. You'll need to tell the rental company which of you will be driving; you should be able to list more than one person, possibly at a charge.

Talk to your own property insurer about coverage for loss or damage while in transit, especially if it's an overnight trip for which you'll need to leave the truck parked at a motel. Which is probably best avoided.

(Incidentally, I would not expect the movers to be "well paid"; apart from the driver, they may be odd-job workers hired for the job at each end of the trip, almost certainly at minimum wage or close to it.)

I'm frankly scared of leaving them out of sight.

You have the reason right there why they won't let you.

Put yourself in the position of the movers. They want to get the job done, they don't care about your stuff anymore than exactly the level of service they offer (varies from mover to mover). The price they quoted you is the price for doing it like they usually do. With a given percentage of breakage and associated penalty. There's also the perception of the boss of how they do it and how they actually do it.

If you go with your stuff:

• You'll want the level of care you expect for your stuff, not the one they expect to give
• You'll nag them non-stop during the ride to be more careful
• You'll know every little dent they may have made to your stuff and ask for penalties, coverage, etc...
• The boss might get to learn, through you, how careful they were, how fast they ride, and how long they stopped in which shady establishment along the way.

Heck, if they were going to check for valuables to "lose", they won't be able to.

There's so many problems, it won't happen. If it could there probably would already be "Move with your stuff and see how nice we are" product available, at a price $$$.

Also consider that many (most?) long-distance movers actually outsource to some random groups of people (typically on the destination side where they may not operate). They probably don't want to outsource moving people and the extra risks.

No. No license.

Because the companies are not licensed to haul passengers for pay.

There are a bunch of rules for that, including collecting data about passengers, ticketing and tariff rules, safety of accommodations, provision of bathrooms, etc. etc. In a Federal country, there will also be rules at the state level for every state transited, so you get a lot of weird problems like "Can't cut the corner through Oklahoma".

Needless to say, being inside the cargo area is Right Out. When stowaways try to sneak in the cargo area, they are often killed by shifting loads.

Complications

Also, a long-distance move will involve stops and driver changes. The next set of drivers might not appreciate the passenger none too much.

Also, because of the human factors, long-distance moves can be quite circuitous. If your load doesn't "cube out" the truck, they may put up a separator and load someone else's stuff behind yours. They may stop at a depot, back your truck up against a wall (so the doors can't be opened) and the drivers head home to their families to sleep in their own bed, and now security has this random person inside the yard to contend with.

Think smaller

Everything I said above applies to general "out of the phone book" long-haul commercial movers. Those guys are full-service turnkey - point them at a house and they will pack up everything in it, and it will show up in boxes in the same rooms in the new house.

There are certainly more informal "movers" that are just "A guy with a truck" sort of deals. They will be much more informal in all respects, and you will have much more flex to negotiate. However, this will shift more responsibility onto you - you will need to buy boxes, pack yourself, and possibly help move furniture. And obviously, the farther you go, the more difficult it will be to get an informal mover.

Honestly, you may be making too much out of the risk here. Nobody wants some random person's stuff. If you doubt that, then go watch some of the TV shows about people who buy random storage units at auction. Those guys are the best in the business at getting value from random personal possessions, and even they can't get much for random stuff.

This is not an answer to the question, but deals with some of your issues.

1. The cost of getting yourself to your new home is likely to be small compared with the cost of moving your stuff. If you can't drive, use public transport.
2. If you find a well-reviewed, long-standing, well-known moving company they will not simply vanish with your stuff. They will also be insured against breakage. Do not worry about this.
3. However make absolutely sure you get a reputable firm to do the move, and get a firm price for it, written down and signed. While companies won't "vanish with your stuff" it has been known for disreputable ones to move your stuff to their storage and then tell you that the price will be much higher than the "estimate" they gave you, and they won't deliver it until you pay. Spend extra money to get a reputable company.
4. If you know someone who can drive, consider renting a moving van and paying them to drive it and help you load and unload. You can then ride with them, and it will be much cheaper than professional movers.

^{(This started out as a comment)}

You are assuming that the moving company only deals with your boxes, and will immediately drive directly from point A to point B in a timely manner once your boxes have been loaded. Neither of those points are guaranteed.

Unless you have enough possessions to fill the entire truck, it is possible you will be sharing load space with another customer's possessions. In which case point to point travel is unlikely to occur. Also if the truck arrives late in the afternoon, it is unlikely to go to the destination until the next day, because the workers won't want to work overtime. Finally, insurance pays for breakage and loss.

It is unlikely that the moving company will have a spot for you to travel with your possessions for a couple of reasons:

1. The truck is likely only going to have room for the people who load and unload the truck.
2. It is unlikely that carrying a passenger is covered by the company's insurance, and they are not going to accept the liability of an uninsured passenger.

However this is all assumptions on my part. The only real answer can be obtained by contacting your moving company and talking it over with them. They may be willing to take you on as a passenger, or they may not. We can't give a definite answer to that question.