Bay seniors who are well aware of the pitfalls of procrastination should sign up now for the one-time-only walk across the entire 4.5 mile Bay Bridge when the new span opens this Labor Day. Space is limited to 15,000 people an hour and 125,000 total. There will be public transportation to the eastern entrance. Do not plan on just strolling on. You will receive a very specific time assignment. Free. On the same site you can sign up for Bridge runs and bike rides.