Labor Saving Effort
Any photographer who has carried props, lighting, clothing, stands, and other camera equipment knows that things can get VERY heavy and bulky even within a fixed studio. Add to this trying to carry equipment, even in a small roller bag over dirt, grass, sand, or mud and your effort is magnified to the extreme. One answer of course is a very strong assistant who will not be very happy, the other is a version of a collapsible roller cart.
There are many companies that put out roller carts but in general the body of the cart is some type of fabric braced on a metal collapsible frame along with large wheels. The better carts have from wheels that will rotate 360 degrees to make the cart easier to push or pull as needed. Most carts will fold with about a 75% space savings when not in use. After a little research, the size of the carts only vary slightly by inches but there is often a steep price jump and shipping costs with certain models.
One deciding factor may be how much weight do you want to put into the cart. Many carts are rate to just over 100 lbs, although some of the heavier cart could even carry a small child. The wheels are larger and of course the metal frame is heavier on the larger carts. Fabrics vary from a canvas style to a light nylon mesh which may be suitable for lighter loads. Most models have an extendable handle which is typically made of lightweight aluminum or in some cases steel. Some models also come with pockets outside of the main body of the cart to allow for things like water bottles, tablets, or any other light weight supplies.
The one notable limitation of these carts is that they will not do well with stairs. While there are carts that will help that will help with stairs, their capacity is much less that as shown above.
Roller cart can be very valuable for the location photographer who may need to travel outdoors with significant equipment. As with anything though, a rain cover can help in the case of an unexpected downpour!