Be bursting/bulging at the seams
Definition 1 of 2
Pro Tip 1/3Physical Crowding
Use it to describe places so packed it's hard to move. 
The train was bursting at the seams during rush hour.
Pro Tip 2/3Beyond Capacity
Suggests a situation exceeding normal limits, possibly to an extreme. 
The shelter was bursting at the seams after the storm.
Pro Tip 3/3Not Literal
An exaggerated expression, not to be taken for a literal tearing. 
With new staff, our office is bursting at the seams.