Date: 201309
Local time of day: 1801-2400
Location: LAS.Airport, NV
Flight conditions: VMC
Light: Dusk
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Descent
Airspace: Class B LAS
ATC / advisory: TRACON L30
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Fatigue; Situational Awareness
Anomaly: Inflight Event / Encounter CFTT / CFIT
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance
Contributing factors: Airport; Human Factors; Weather
Primary problem: Airport

Narrative: We were on the KEPEC arrival into LAS and were planning to execute a visual approach to Runway 7R per the digital ATIS there is no published approach for that runway so we 'built' one with a 5 NM final and a three degree glide slope. We planned on being at 3;800 MSL at that point for the approach. During our briefing we discussed the terrain west of the airport and noted the illusion due to the sloping terrain. This is not a usual runway for landing and I've only used it two times before in previous years.The KEPEC arrival is intended to be used for runways 25L and 25R arrivals and [published crossing] altitudes are high as expected for the terrain in the area. LAS approach cleared us down to 7;200 and for a visual approach to Runway 7R. As we neared the airport we were asked if we had the field in sight and responded 'yes' as the city and airport are easy to identify due to the bright lights. It was almost dark. We were around 15 miles from the airport when we were cleared for the visual approach to Runway 7R; we were given a heading to intercept final which came pretty close the 5 NM final fix we had created. Our vertical navigation indicated a descent of around 1;300 FPM to reach our planned 3;800 at that point.We started our descent and soon thereafter ATC called us with a low altitude alert on their screen. We immediately leveled off; verified our position and verified with ATC that we did have the airport in sight. I was in terrain mode and knew of the terrain to the left west of our position and the terrain ahead was 'green' on the NAV display. We maintained altitude around 5;500 until assured of terrain clearance and continued the approach with out further ado. We were vectored below the altitudes on the KEPEC arrival. It was probably too dark to accept a visual that far from the airport. There is some high terrain to the southwest of LAS and descents should be made much closer to the airport and may require much greater rates of descent than normally used at other airports. It is very desolate to the southwest of LAS there are no lights of any kind no houses; no roads other than a highway and depth perception is lost; kind of like descending over a large body of water at night. The high overcast probably made it much darker than normal.I would like to see a charted visual approach with recommended altitudes for times when LAS is using Runway 7; or; maybe; a maintain XXXX FT until XX DME from LAS. I realize that Runway 7R is almost never used but I would like to see some sort of guidance to make those approaches easier and safer especially after almost 12 hours on duty.




Synopsis: A B737-700 flight crew arriving LAS from the west as dusk was turning to night was cleared for a visual approach to Runway 7R. During their descent they received a low altitude alert from ATC as they crossed terrain as high as 8;600 MSL.