Updated Aupgust 4, 2023
Unless cruising the Strip is your afternoon or evening entertainment, it's best to avoid it in a car anytime. But it's especially wise to take the shortcuts at prime times -- from 5 till midnight every night and 24/7 over the weekends. The shortcuts run parallel to the Strip (north-south) and across the Strip (east-west).
There are two good alternate north-south routes west of the Strip. One that was completed in 2004 is Frank Sinatra Drive, which runs between I-15 and the parking lots/garages of Mandalay Bay, Luxor, New York-New-York, Park MGM, Bellagio, and Caesars Palace. It connects with Russell Road to the south and Dean Martin Drive (formerly Industrial Road) to the north. (To get off in between, you have to drive through parking lots.)
Speaking of Dean Martin Drive, this service road also runs parallel to the Strip, but it's west, on the other side of the freeway. It continues far south of the tourist corridor, but the most useful stretch is from W. Hacienda (where a bridge crosses I-15 and delivers you right to the Mandalay Bay parking garage) up to W. Twain, where it crosses under the freeway and merges with Frank Sinatra Drive to become Sammy Davis Jr. Drive. It runs north past the back of the Mirage, Fashion Show Mall, Trump International, Resorts World, and Circus Circus, then runs under Sahara Avenue where it turns into Industrial Road. When it crosses Charleston, a newish road, S. Grand Central Parkway, runs up past Symphony Park and goes through the "back door" to downtown.
On the east side of the Strip, you should learn the Koval-Paradise parallel route from Tropicana to Sahara avenues. From Reno Avenue (it intersects the Strip between Luxor and Excalibur), you can follow Reno around to the north (left) onto Koval. From there, you can hit the back doors of all the casinos on the east side of the Strip from the MGM Grand to the Venetian. Where Koval ends, do a dogleg right (east) on Sands Avenue, then left on Paradise, from which you can access the Convention Center, Westgate, Sahara, and Strat.
Crossing the Strip on east-west thoroughfares can be brutal. The fastest way to get from one side to the other without touching it is to make use of the three-mile Super Arterial, which connects Paradise on the east to Valley View on the west via the six-lane no-lights Desert Inn Road. This shortcut is extremely convenient if you’re going from the Orleans, Gold Coast, Palms, or Rio to the Westgate or Virgin.
The second best option for crossing the Strip is Spring Mountain Road (west) and Sands Avenue (east) between the Fashion Show Mall and Treasure Island. Spring Mountain Road is often five times faster than trying to cross the Strip at Flamingo Road. And it’s only a long block away, the next large cross street north.
Tropicana Avenue is also preferable to Flamingo for crossing the Strip. If you can, avoid crossing the Strip on Flamingo, especially westbound past Bally's. There's always a bottleneck there.
Sahara is a good way to cross the north Strip.