On the "back" of Frenchman Mountain is a very steep dirt access road that is used to service the radio repeaters at the summit. Following this road is the most foolproof way to hike to the summit, since there is no way you can lose the trail, even at night. The main disadvantage of this route is that you can't see much of Las Vegas until you reach the summit.
This is an extreme 4WD road, with some very steep grades. The drive up looks challenging, but not nearly as frightening as driving down. There is a gate at the start of the road, but it has been repeatedly broken through, probably by offroaders. We don't recommend driving, even if the gate is open.
To hike, the road is not dangerous. It is, however, very steep for most of its 1.5 mile length, and it is a good workout for the legs. On the way down, you have to walk with baby steps to avoid falling on your derriere.
You can hike this route at night. There is a good deal of ambiant light from the city, but you will want a flashlight to assure better footing on the way down.
The road is accessible from Lake Mead Boulevard, which runs between North Las Vegas and Lake Mead.
From I-15, exit at Lake Mead Blvd East. (This exit is north of downtown Las Vegas and should not be confused with Lake Mead Drive, which is on the southern edge of Las Vegas.) Go east on Lake Mead Blvd through a dense urban area for about 8-10 miles until the road reaches a pass. As you approach the pass, the mountain on the right is Frenchman Mountain, and the one on the left of the pass is Sunrise Mountain. The access road to Frenchman Mountain is on the right about 1 mile beyond the crest of the pass (or 2 miles beyond Hollywood Blvd., the last major cross street). The road should be obvious, snaking up a hillside.
There is plenty of parking in the desert at the base of the road.
The road is very steep and probably very dangerous to drive, but it is safe to hike. The slope of the road is close to the maximum that a 4WD can handle, so it can be hard on the legs when hiking. The road climbs steeply for about 1200 vertical feet through a ravine, drops down about 200 feet to a saddle, then climbs 600 feet to the summit.
No special equipment required, but a flashlight or headlamp is useful at night. Don't forget to bring adequate water.
See Jim Boone's Frenchman Mountain page for many details and photos on this route.