To make the best use of the best available information on street lighting for safety, Santa Fe should hire a Professional Engineer, or Engineering Consultancy, that is expert in street lighting and sensitive to its affect on city ambience.
Street Lights and Safety
Why Street Lights?
The principal purpose of roadway lighting is to allow accurate and comfortable visibility of possible hazards in sufficient time to allow appropriate action to be taken.
That’s true whether one is talking about drivers, or cyclists, or pedestrians, or kids playing in the street.
It’s true whether the road is a major street, like Cerrillos, or a residential neighborhood street.
It applies to the feeling of security that you experience when you are out walking.
And, it applies to your actual security, which may be different than how you feel!
Who are the street lighting safety experts?
In the United States the street lighting experts are the Illuminating Engineering Society (IES).
The IES works closely with the National Highway Transportation Safety Administration and state departments of transportation.
Together, they carry -out research into lighting and safety, and pore over research conducted by others in the United States and throughout the world.
Periodically they publish standards – expert, consensus assessments of the best practices in roadway lighting for safety – which are relied upon by certified Professional Engineers (P.E.s) throughout the country to guide the design of the safest roadways.
What do the experts say?
The most recent standard – RP-8-18, published in 2018 – makes several important points about roadway lighting, its appropriate brightness, and color temperature:
- For traffic safety color temperature – “Kelvin” – doesn’t matter.
- For traffic safety you need to get the brightness right. And, the brightness you need doesn’t depend on the color temperature, either.
- On most streets with a posted limit < 30 mph headlights are enough. On these streets, you can choose lighting for resident comfort.
A secondary – but still important – safety concern is the ability of a driver or pedestrian to recognize different colors under a streetlight. Experts call this color rendering. Better color rendering means greater roadway safety and a greater feeling of comfort and personal security.
With previous streetlighting technology low color temperature lighting was poor at color rendering. This led designers to choose higher color temperature lighting, which – for this older technology – offered better color rendering ability.
Modern commercial LED street lighting offers superior color rendering at low color temperature: color rendering is no longer a reason to choose high color temperature
THe Bottom Line:
Streetlighting for safety depends only on choosing the right brightness for the speed and kind of traffic carried by the road, or the nature of the roadway intersection. The brightness needed for safety does not depend on streetlight color temperature. A street light plan is free to select the spectral content of the street lights to address city ambience, the environment, public health, or other concerns, all without sacrificing safety.
But What about accidents on Airport Rd, St. Francis, Cerrillos, Etc?
Roadway safety of all kinds is of vital importance. To prevent accidents we need to know what causes them. Only when we know what causes accidents on Santa Fe City roads will we know how to prevent them.
What are the causes of accidents on Santa Fe City roadways?
In Santa Fe (and all New Mexico municipalities) all traffic accidents are reported to the New Mexico Department of Transportation (NMDOT) on a State of New Mexico Uniform Crash Report (NM Statute 66-7-209). Included in the information reported is the lighting at the time of the accident (including time of day and roadway lighting) and apparent contributing factors to the accident. Apparent contributing factors include visibility conditions. From this information NMDOT compiles aggregate statistics statewide and for every community, including Santa Fe City. You can find these reports here.
The most recent report for the City of Santa Fe is from 2019, and is available here. Table 15 of this report lists the frequency of contributing factors in all traffic accidents, both in aggregate and by crash severity. In 2019, no crashes in Santa Fe were ascribed to lighting or visibility conditions. Over all of 2019, the top three accident causes identified by police were, in order, following too closely (25%), driver inattention (20%), and failure to yield right-of-way (16%). Brighter lighting, or higher “color temperature” lighting, would not reduce accidents associated with any of these causes, which amount to over 60% of the accidents on Santa Fe City streets.
Traffic safety is necessarily a matter of the greatest concern. To best address traffic safety, understanding the cause of accidents is crucial to identifying the most effective means of reducing them. Guessing is not good enough. We urge that city of Santa Fe hire a Professional Engineer, or engineering consultancy, that is expert in traffic safety to evaluate the causes of accidents and advise it on the appropriate measures to take to protect its residents.