One element of driving defensively is driving to save money. Taking good care of your vehicle can pay cash dividends, and you'll be much less likely to get stranded out on the road where you'd be vulnerable to a variety of calamities. "The devil is in the details"—ever heard that phrase? Most often, what stops you cold is a simple thing. Before a road trip or once a week (or whatever interval you choose), spend some time maintaining your vehicle—like your TIRES, for example.
Your tires should have plenty of tread. If they don't, replace them. Use the "Lincoln Test." Insert the head of a penny into the tread of your tire—the top of Mr. Lincoln's head, first. (He won't mind, he's been dead for awhile.) At least part of the top of Honest Abe's head should disappear into the tread—if it doesn't, your tires likely need to be replaced. Not only does worn tread affect your vehicle's handling and increase your risk of hydroplaning, but worn tires pick up road hazard damage much easier than good tread. Worn tires equal more flats—that's the rule. Many newer tires have "wear bars" that show up when tread is worn, so watch for those as well.
Correct inflation is extremely important for a couple of reasons. Your automaker designed the suspension and handling of your vehicle for a particular size tire, inflated to a specific pressure. Unless you are an engineer who's adept at understanding the physics of whatever changes you make, don't do it. Tire pressures should be set to the pressure specified by the manufacturer, NOT the maximum pressure embossed on the side of the tire. A tire is made for any number of vehicles and different pressures (up to the maximum) are required for different applications. Set them to what the maker says is correct. They've designed your vehicle for that pressure, and that's where it will handle best.
Want to save a load of change? You can waste one third of the tread life of your tires by running with them 10% low on air. Take four tires at $130 each. If the correct pressure is 36 lbs., but you consistently run them 3.6 lbs. less than that, you stand to lose $43 worth of tire to excessive wear, each tire. That's $172 of your hard-earned cash you threw away for want of an air gauge and some initiative on a Saturday morning. Folks who know say most of us are running with lower pressure than we should be, often more than 10% low, because we don't check them often enough.
How does low tire pressure affect vehicle handling? It's not a pretty picture! Low pressures adversely affect braking performance. Low pressures also can affect your ability to steer and corner. You can do yourself a huge favor by simply spending five or ten minutes each week with your tires. Remember that all tires lose air over time, and temperature affects the pressure. The colder the weather, the lower the pressure in your tires. Be sure to check them once every week or two. Use a good air gauge, and check them when they are cold—first thing in the morning when you haven't driven more than a mile or two.