Road conditions vary from city to city, but here are some universal facts: 169,278 hours and 120,127 gallons of gas are wasted by Americans in traffic each year; 81 percent of fatal car accidents happen on rural roads; and 32 percent of traffic fatalities involve drunk drivers. For commuters, traffic is invariably worst on Fridays from 5 to 6 pm and best on Mondays. With all of that said, here are the 10 trickiest pieces of pavement to negotiate in the nation. Avoid at all costs.

Los Angeles 101 to I-405 Interchange

Click to enlarge pictureLos Angeles Highway 101 to I-405 Interchange (© Microsoft Live Search)

Los Angeles Highway 101 to I-405 Interchange

Nowhere in the nation (except parking lots) do cars spend so much time bumper-to-bumper than at the juncture of the 101 and 405 freeways in Los Angeles, which link the east side of the city with the downtown area. The statistics alone are enough to provoke road rage: 318,000 drivers per day use this juncture, and they spend 72 hours of their lives stuck in traffic annually. The rush hour window here is a staggering five to eight hours per day, and during that time, you'll spend twice as long on the road as when it's traffic-free — which makes for the highest travel time index rating in the nation. If you must drive it, make sure your Bluetooth is fully charged and your iPod is locked and loaded. Speaking of which . . . you'd be wise to avoid eye contact with other drivers: Car-to-car shootings are not a relic of the past. There have been six so far this year, although most were the result of gang violence rather than road rage. If your schedule is flexible, log on to www.sigalert.com for a personalized traffic report that includes e-mail updates on your route and a traffic-camera video feed.

Colorado 550, aka Million Dollar Highway, from Ouray to Silverton

Click to enlarge pictureColorado Highway 550 (© Microsoft Live Search)

Colorado Highway 550

This southern Colorado two-laner is all-around treacherous: As it climbs out of the former mining town of Ouray, the southern route S-curves through three San Juan Mountains passes (topping out at 11,018-foot Red Mountain Pass) with nary a guard rail or sliver of shoulder all the way to Silverton, 24 miles away. Fleets of road-hogging recreational vehicles routinely make this drive, giving you zero room for error, and late fall's wildlife migration and deer hunting season put thousands of deer and bighorn sheep on the move and crossing roadways unexpectedly. Ice slickens 550's pavement as early as October. During winter passage it is even dicier: The Million Dollar Highway is directly in the path of a major avalanche zone, and in 1987 the road was buried by a slab avalanche. For current Colorado road conditions, visit Colorado's Department of Transportation at www.dot.state.co.us.

Atlanta's I-285 at I-85 Interchange, aka Spaghetti Junction

Click to enlarge pictureAtlanta I-285 at I-85 Interchange (© Microsoft Live Search)

Atlanta I-285 at I-85 Interchange

The hip-hop duo Outkast, Atlanta natives, named a song after this gnarly web of highway. The lyrics are foreboding: "Be careful where you roam cause you might not make it home. Don't you dare ever get lost cause you get caught up in that sauce." The junction is a five-level interchange (think clover leaf above clover leaf above clover leaf) with multiple ramps and smaller roads feeding into it. The American Highway Users Alliance gave Spaghetti Junction a grade of F, indicating that stop-and-go traffic prevails here most of the time, causing 133,000 hours of traffic delays each year. The time to avoid Spaghetti Junction at all costs: in winter, when a combination of rain and freezing nighttime temps can turn the many ramps and overpasses into a labyrinthine ice skating rink, causing dozens of accidents and epic delays.

San Diego, I-5

All-you-can-drink specials at Tijuana bars attract hordes of SoCal residents each weekend — many of them San Diego college students and other minors who are lured the 15 miles across the border by Mexico's lower drinking age (18). Hence, the stretch of Interstate 5 leading north from Tijuana becomes a swerving, high-speed DUI minefield on weekend nights, and each year 10,000 to 15,000 people are arrested for driving while intoxicated in San Diego County. Occasionally, all-night binges combine tragically with one of the most traffic-clogged early morning commuting routes in the country — both in San Diego and leading north through Orange County.

Chicago, Circle Interchange

Click to enlarge pictureChicago Circle Interchange (© Microsoft Live Search)

Chicago Circle Interchange

When this highway interchange was originally built in downtown Chicago in the 1950s (linking I-94 and I-90 with I-290), the idea was that the complex of single-lane, circular on-ramps would slow the city's traffic to 25 miles per hour so that drivers could merge peacefully into six-lane highways. Fifty years later, as Chicago's population has blossomed to 2.8 million, the Circle Interchange has put a stranglehold on Windy City commuters, who endure an average of 90 minutes of traffic delays on it each week. The Circle Interchange's prognosis is grim: This tangle of roads was built on a four-square-block plot of land, which makes improvements a civil engineering conundrum. Making matters worse is that I-290 is a traffic nightmare in its own right, moving at an average speed limit of 11 mph during rush hour.