Strength
Strength
is a fundamental skill that allows you to carry more items at a given time. Specific jobs rely heavily on your Strength level. Per level, you unlock an extra 10KG of weight.
It is currently the only skill that is capped at level 30, meaning your max inventory capacity is 300KG (345KG with Premium). Using trailers and trunks you can go far beyond this limit. Trailers are also essential for advanced trucking routes.
Earning Strength Experience
Cargo related jobs (such as Trucking and Cargo Pilot) rely on you having a big inventory capacity. Certain jobs and activities in Transport Tycoon will earn you Strength experience to be able to carry more items.
Trucking
Trucking is the first skill most players come in contact with that also gives Strength experience. Erasers' small weight combined with its decent XP per item makes it the fastest method of obtaining Strength experience, compared to other Trucking Cargo.
Specialized Jobs
Besides trucking, most Specialized Jobs will also reward the player with Strength experience:
UPS
In the UPS Job you deliver packages to houses, warehouses and stores. Upon delivering you earn Strength, Player & Trucking experience. Finish the route for a bonus.
Transformer Repair
When repairing transformers you will earn Strength,Player & Mechanic experience.
Server Repair
As with the Transformer job, repairing servers will result in Strength,Player & Mechanic experience.
IAA Delivery
Delivering Coffee and Documents to IAA employees will give Strength & Player experience.
Mining
Mining at the quarry will give Strength & Mining experience.
Gym Vouchers
Gym Vouchers can be found in Treasure Chests 
and will grant Strength experience when redeemed at the Grand Exchange.
