It's not as much later in the day as it is later in the rush. If you head out at 10:30am, traffic will be around the same as 6:00am. This is true until around 2:30, when it starts turning to shit again. The afternoon-evening rush is worse, and lasts longer too.

And, sir, that was a chart not a schematic. With the new boss I have, we've learned first hand about charts. Although yours was for the benefit of others, so it's in a slightly different class from the ones I'm used to.