Have you heard of the 'Scotopic Advantage'  with LED lighting ? 

Scotopic Advantage  began with LED streetlights, and became a popular phrase to help promote LEDs as a lower luminance replacement for conventional lighting; Scotopic is related to Mesopic.  You may hear that LEDs are rich in Scotopic Lumens.

See this article about an LRC Mesopic Streetlight Project (Article in PDF).  More about Mesopic later.

Pay particular attention in this article to Dr. Mark Rea's comment:
Dr. Mark Rea, director of the LRC, says mesopic lighting conditions occur at night in areas with low lighting levels. "Humans see very differently under mesopic conditions than under photopic or scotopic lighting conditions," says Dr. Rea. "Photopic conditions occur during the day and in lit buildings, while scotopic conditions occur at night under the stars."

LEDs can be tailored to almost any color temperature, and they bring Mesopic color into a reasonable price range; it stands to reason they will make superior streetlights over the conventional technology. 

Background:  Photopic vision is the term for Human visual response to daylight, or luminance of ≥ 3 cd/m² (candela per square meter).  Our Photopic color sensitivity is highest with green.  Scotopic vision occurs at a luminance level of about 0.01 cd/m² or less; that color sensitivity peak is blue. 
          See Wikipedia on Scotopic Vision.  (Also note Mesopic Vision while you're there.)
Mesopic vision defines the sensitivity shift between Photopic to Scotopic, in which our color sensitivity shifts from green to blue respectively as luminance is reduced.

Now you know that Mesopic vision occurs with luminance levels  < 3 cd/m².  For an equivalent, that's about 3 footcandles of illumination.  Scotopic Vision does not occur during daylight, or with ordinary room illumination indoors, or with outdoor lighting of 3fc and higher (stadiums, gas stations, car lots, etc.). 

The problem is, the Scotopic Lumen  spin is used to hopefully convince you that less LED footcandles can do the same job as higher footcandles at a lower color temperature.  The truth is, there is no Scotopic advantage to ANY lighting if your requirements are 3 or more footcandles.  At 3fc illumination, the rods are overwhelmed, the cones in our retina do all the work; that's Foveal Vision. 

Perhaps the first fallacy of applying a Scotopic Advantage where safety is an issue is accounting for the time requied for our vision to adapt to darkness.  That adaptation period may require 10-minutes, and then a flash of bright light, e.g. car headlights, etc. will reset our 'dark adapted vision'.  Then we must wait to see again. 

    At this time, the IESNA has NOT incorporated Scotopic effects into its lighting recommendations.

In actuality, illumination with a higher CCT (cooler) light will appear  brighter than an equivalent power lower CCT (warm) light when it's better aligned with our Photopic Visual response.  But, going too high (cool) it will appear less bright again, as shown in the following explanation.

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The graphs of Figure 1  plot our visual response.  
Figure 2  relates the spectral output of two popular color temperatures, cool white and warm white. 

Comparing two colors in the Photopic range, 555nm (nanometer) and 610nm (warm white) for example, 610nm is perceived as only 50% as bright as 555nm. 

A light source of 525nm (blue-green) will be almost twice as bright as 610nm (warm white).

The Photopic curve shows that an equal level light source more blue than 510nm will also appear to be as low in brightness as 610nm while at Photopic luminance levels.

In summary -
At luminance levels of 3 cd/m² and higer, our vision is with cones, the rods have little or no response.  This visual response is entirely Photopic. 

Our 'dark adapted vision' is a function of lower luminance over time.  Always consider the safety aspect of the application;  i.e. how quickly does one need to see in a lower luminance environment?

In Physics and light measurement sciences, the Photon is a unit of measurement of light.  LEDs have no magic beams. 

This topic is not specific to LEDs or any other technology.  Any lighting color that is properly aligned with our visual response is more efficient than lighting that is not; it will appear brighter.