In general, cycling is very safe. Of course you have to keep your eyes open, but unless you're weaving through cars, doubling the speed limit, or texting, you probably won't have any problems. I see old ladies cruising in Brooklyn all the time, and they're doing just fine.
That said, there are a few things you can do to stay alive on the commute home, because well, cars can kill you. (The whole "high-viz" argument has recently been discussed, where retired cyclist Chris Boardman said he wouldn't support high-visibility clothing and helmets because it focuses on the symptoms and not the cause of cycling accidents.)
Point taken, but it doesn't hurt to do what you can in order not to be hit. And now that it's winter, you're probably going to be doing a hefty amount of riding in the dark. Here's a roundup of the things that can help you avoid incident.
Zap Bike Jacket - $160
Most high-viz bike jackets look ridiculous in normal settings—neon just isn't for everyone. Sugoi's solution to this problem is ingenious—they use a fabric composed of tiny reflectors that light the jacket up like a Christmas tree when struck by a headlight. So you can have a black or red jacket under normal light and a reflective beacon when you're on the road.
Spurcycle Raw Bell - $39
Regarded as the Rolls Royce of bicycle bells, this tiny gizmo will mount to almost any handlebar and is the next best thing to getting an air-horn for your bike.
Torch T1 Helmet - $150
There've been plenty of bike lights that stick onto helmets, but Torch takes it to the next level and integrates 10 LEDs into theirs. It charges via USB, has plenty of vents, and makes it impossible for you to forget your lights. Even if you have the Torch, we recommend you using it in conjunction with another light.
Disc Brakes - $Various
If you're buying a new bike, you might want to consider disc brakes. Stopping on dry rims is fine, but when the elements rear their ugly heads, you might find yourself skidding into an intersection. Some of us—myself included—use general caution instead of disc brakes, and it's usually fine. But if you're getting a new whip, the option's something to consider. They're available from Shimano and SRAM in hydraulic or mechanical discs.
Giro Savant MIPS Helmet - $110
If the Torch doesn't really jive with your steez, the Savant is another great option. The first Giro road lid with MIPS technology—essentially an extra shell that slips, slowing your head's deceleration—this helmet puts another layer of technology between your head and the pavement. It features Giro's trademark good-looks as well.
ICEdot - $119
This small, helmet-mounted button will notice if you crash and initiate an emergency call unless you take out your phone and abort—just like a house alarm. It'll also broadcast your GPS coordinates so your friends know where to find you if you need help.
Lezyne Micro Floor Drive HP/HPG - $44-59
The infinite strokes of your mini pump might warm you while stranded on the side of the road, far from a subway station, but there's something far better. In a stroke of genius, Lezyne created a tiny floor pump that's about the same size as a standard mini-pump, just small enough to fit into a jersey pocket. Except, of course, it works really, really well since you can put a foot on it. With a built-in pressure gauge on some models and a threaded adapter that will get a good grip on your valve, it can easily hit 120 psi—we didn't dare go higher—making it the best reasonable alternative to a personal SAG wagon.
Light & Motion Urban 500 - $100
Lights do two things: They illuminate your way and notify cars of your presence. Light & Motion's USB lights do one of the best jobs at that that I've ever seen. Besides simply shining front-ways, they have yellow windows on the sides, giving you that essential side-visibility. The Urban series is available in a several different lumen numbers—500 is enough for the city, but you might want to bump that up slightly if you're in a rural area. Additionally, they let you know when they need a charge and are easy to take on and off. Their rear lights are on point too for $45. Call it insurance.
Continental Cyclo X-King - $40
If you're rocking the commuter or cyclocross bike with road slicks, it might be a good time to swap them out to get a little more grip. Built for 'cross courses with a little bit of everything, the Cyclo X-King's will have no problem handling whatever your commute has to throw at you this winter.