Yes, Yes, Yes, Yes and Yes!
We always advise to give yourself PLENTY OF TIME to account for traffic. Accounting for traffic, buses, etc is YOUR responsibility.
Once the group starts, they will NOT allow you to enter, and you will NOT get paid.
Think of it as a job interview. Would you be late to a job interview?
You HAVE TO SHOW UP ON TIME!
Be there 15 minutes early for paperwork. ALWAYS!