There are things the city could do to ease traffic flow, as has been noted here and elsewhere, synchronizing lights and adequate intersection signage come to mind, but a lot of problems could be reduced by individual actions.
In a city with many unmarked intersections in residential areas, one of my favorite offenders is the Braketester. This fellow waits until the last moment to begin slowing, leaving the driver with right-of-way to wonder a) does he know I'm there; b) does he care; c) are his brakes good if both the above are affirmative?
A close cousin is the Tailgator. This charmer pulls up behind me like he is trying to "draft" in a NASCAR race. He needs a sign (printed in reverse for rearview mirrors) reading "What are you doing on MY road, you old fart?" Curiously, said Tailgator is just as common on the fourlane where he could easily pass. On bad hair days, I am tempted to discover a stray cat whose presence demands an emergency brake on my part. Given the extra-stout towing package bumper on my rolling antique, I would be driving my dented, but servicable vehicle off while Tailgator is getting written up for a ticket and waiting for a tow.
Being the cautious sort of driver more likely to attract a Tailgator than to be one, I am not about to criticize anyone going perhaps a bit under the speed limit. There is one variant on this who contributes to the profits of makers of hypertension drugs. After patiently following this driver for a mile or few, I find an open lane or a four lane section and pull out to pass. Suddenly, the driver I have been tracking at 45MPH is impossible to pass at 60. This one needs a sign reading "I may not be fast, but I shore love to be in front."
We have moved to the point on intoxicated driving that people on the marginal edge are afraid to drive home from a dinner out after a glass of wine. I see people way more dangerous during the morning drive. They are tooling down the road, cell phone in one ear and hand, and/or finishing the morning grooming on the fly while navigating more or less across a couple of lanes in the day's busiest traffic. They need signs, front and back, "Just riding behind the wheel", so the rest of us know to give them lots of room.
By all means, the city can, and needs to, keep working on infrastucture, but we as users of it can help by paying attention. Helpful hint: pretend the cars close to you are piloted by armed former postal employees.