Negative Effect of Driving from a Lighted Street is not Bogus

by Rod Veach, West Sedona

Sedona, AZ (November 5, 2011) – On Thursday November 3, 2011 Dr. Serge Wright (speaking for Let The People Vote) at formal public debate (OLLI Lunch and Talk) used the term BOGUS when asked to address the potential negative effect of driving from a lighted street (potentially W 89A if Continuous Roadway Lighting is installed) onto a totally dark street (all of Sedona’s side streets). Mr. Wright provided an explanation of why transitional lighting is not an issue. To an unknowing person what Mr. Wright said seemed completely logical. He said that because the lights were 35 feet in the air we would not have a problem. Think about this. The lights are designed to light the roadway where we are driving. If we don’t have enough light on the roadway surface to worry about, why bother with the installation of the lights. My thought is that his answer was completely fabricated. I hope Mr. Wright has the courage to read this and respond to what he has read. I am not a lighting expert, but the information below demonstrates that transitional lighting is not a BOGUS issue. Real experts in highway lighting design believe it is an issue that requires attention. Mr. Wright has the credentials to help people with their vision issues, but he certainly cannot debunk what highway engineers, trained in that field, say about how a highway lighting system should be designed.

“Transitional lighting” is a lighting term that refers to the need for a transition between lighted and dark areas. When driving from a lighted area (West 89A if streetlights are installed) into a dark area (all Sedona side streets), a driver’s eyes require up to fifteen seconds to adjust to the new light level. While this adjustment is taking place, the driver’s vision is impaired, thereby creating a perilous situation. Older drivers’ eyes find it more difficult to adjust in this transition zone. This lack of transitional lighting is a serious issue for West Sedona, which has more than 30 unlit side streets, most without sidewalks. Imagine, if you will, an older person turning onto a dark side street and struggling to see, while someone is walking on that dark street. ADOT is willing to create this situation in order to install continuous roadway lighting, attempting to address a nighttime issue that does not exist.

If the City of Sedona accepts CRL after understanding the safety issues involved in transitions from lighted to dark streets, it necessarily increases its liability.

The FHWA and numerous state DOT’s, including ADOT, recognize that if transitional lighting is not provided, an unsafe condition is created (see information below). Even though ADOT’s Engineering Practice regarding highway lighting (Section 700-Illumination) specifically refers to the necessity of transitional lighting in a situation like West 89A, ADOT is refusing to address this issue. To provide transitional lighting, several hundred feet of each side street would need to have streetlights installed, lighting up the whole town, truly not a desirable solution. Even if it were desirable, ADOT does not own the side streets, the City does. The cost of lighting side streets to address this problem of transitional lighting for approximately 15 miles is huge. (ADOT Engineering Practices recommends ½ mile of transitional lighting per street, and Sedona has 30 side streets). So the streets would stay dark, and the problem remains unresolved.

By installing CRL, ADOT is actually making Sedona more dangerous.

The following information fully shows that transitional lighting is not a BOGUS issue. As can be seen from the data collected by doing a simple internet search, there is nothing BOGUS about transitional lighting. It is real, and presents a real danger to all drivers, especially older drivers.

(Websites are in blue, authors comments are in green and quoted text is dark red.)

Below you will find information relating to engineering policies for the installation of continuous roadway lighting in those situations in which the newly lighted roadway would be contiguous with dark streets or roadways.

Information directly below is from the ADOT website verbatim.

ADOT Traffic Engineering Policies, Guidelines, and Procedures January 2003

Section 700 – Illumination

700-3

b) Continuous Lighting on Conventional Highways

Continuous lighting on conventional highways is considered to be

justified where local agencies find sufficient benefit in the forms of

convenience, safety, policing, community promotion, public relations,

etc. to pay the cost of installation, maintenance, and operation of the

lighting. Continuous lighting may be permitted by the State after the

consideration of the following conditions: [highlighting mine]

1. Is lighting on a city street grid visible from highway?

2. Are the cross streets lighted up to one-half (1/2) mile in each

direction from the highway?

3. Is the area under consideration urban?

4. What is the night time number of crashes vs. the day time

number for that section in the past three (3) years?

_______________________________________________________________________

You will find data from different state agencies, municipalities, and from FHWA below.

Richmond.ca/_shared/assets/roadway_lighting20126.pdf

6.8 SPECIAL CONSIDERATIONS

Illumination levels differ for different classifications of roadways and where these roads meet

there shall be a transition area. The road with a lower illumination level shall have a gradual

increase in illumination level until the higher level is reached.

/www.ottawa.ca/residents/planning/design_plan_guidelines/completed/lighting/chapter2/2_11_en.html

2.11 Transition Illumination

________________________________________

Where sections of roadways that are fully illuminated are located adjacent to sections that are not, the street lighting shall be transitioned as recommended by the Guide for the Design of Roadway Lighting2 Transitioning of the roadway illumination will allow for easier adaptation of the driver’s eye from a lit to a dark section of roadway. A consistent style of lighting equipment will be used in the transition area selected from Appendix B Approved Lighting Equipment.

2.11.1 Full Continuous Lighting up to a Boundary Road

For unique situations where an urban road designation is being fully illuminated up to the boundary of an urban / rural area, the full illumination shall be transitioned as recommended by the Guide for the Design of Roadway Lighting2. The transition illumination will be extended into the rural area up to and including the point where the roadway tapers from an urban cross section (four lanes with curb) to a rural cross section (two lanes without curb).

2.11.2 Transition Illumination at Intersections

For intersections where only one of the intersecting roads has full continuous lighting and the light levels at the intersection are 50% greater than the light levels of the approaching illuminated roadway (as required by Section 2.3 Intersections), the non-illuminated intersecting road shall have transition lighting designed to extend the lighting beyond the intersection with a maximum of two pole cycles for each approach.

www.gogreenva.org/assets/docs/7_ArlingtonStLight.pdf

ARLINGTON COUNTY GOVERNMENT

STREET LIGHT POLICY AND PLANNING GUIDE

3.4 TRANSITION LIGHTING

When developing lighting plans, the effects of lighting on the driver’s eye must be

understood. According to the “Roadway Lighting Handbook”, a driver’s eye

adjusts every time it experiences a lighting change. It is more difficult; and takes

longer for the eye to adjust from light to dark than conversely. With this in mind,

the handbook specifies that a transition lighting section be provided when moving

from one light level to another.

The Illumination Engineering Society recommends that the light level be reduced

by no more than 50% in a section of roadway that a vehicle travels along in a 15-

second period. This means a driver traveling along the roadway would

experience no more than a 50% drop in illumination in 15 seconds. This rationale

will be considered when going from any type of zone in Arlington, like going

from a commercial area along a residential street into an intermediate or a lowdensity

area. This insures there is uniformity, and does not compromise this design imperative.

ntl.bts.gov/DOCS/97095/ch02/body_ch02_04.html

The objective was to determine the extent to which transient visual adaptation (TVA) affects drivers’ detection of targets along partially lighted freeway interchanges. TVA occurs when the eye moves from one luminance level to another and is continuously adapting to higher and lower levels, thereby temporarily reducing contrast sensitivity. A reduction in contrast sensitivity can reduce the probability of detecting a target on the road or roadside.

www.modot.org/design/ppdm/files/801.pdf

8-01.4 (2) (d) ADAPTATION (TRANSITION) LIGHTING. Adaptation lighting attempts to reduce the rapid and extreme changes in levels of illuminance which occur when entering or leaving a continuously lighted section of roadway. Adaptation lighting is also used to adapt the driver to continuous interchange lighting before important decision points. The value of adaptation lighting is debatable since it is difficult to attain a gradual uniform change. Adaptation lighting is recommended for the extremities of a continuous lighted section of roadway that is a mile [1.5 km] or more in length or complex interchanges that are continuously lit. The transition effect is attained by decreasing the intensity of the last few luminaires, rather than by using increased spacing. Typically, the transition section is 15 seconds in length and the average intensity is approximately 50 percent of the intensity in the continuously lit section

www.northbrook.il.us/files/SOP%20TEXT/SECTION(6).pdf

O. TRANSITIONAL LIGHTING SECTIONS

Roadway lighting systems shall be designed to decrease the driver’s brightness when

emerging from a lighted section of roadway. Using the design speed of the road, the

reduced lighting level zone with smaller lamp sizes shall allow for a ten (10) second eye

exposure adjustment.

www.mdt.mt.gov/other/traffic/external/pdf/chapter_13.pdf

5. Transitional Lighting Transitional lighting is a technique intended to provide the driver with a gradual reduction in lighting levels and glare when leaving a lighting system. The designer may consider transition lighting after a study of the conditions at a specific location. Typical transition lighting design should extend the lighting system a sufficient distance beyond the normal limits of illumination.

www.tdot.state.tn.us/Chief_Engineer/assistant_engineer_design/design/Traffic_Design_Manual.pdf

4. Transition Lighting. Transition lighting is a technique intended to provide the driver with a gradual reduction in lighting levels and glare when leaving an illuminated area. Several implementation methods exist.

The designer also may consider extending delineation 1000 ft beyond the last luminaire for traffic lanes emerging from a lighted area (ambient light). This will provide an additional measure of effectiveness.

Vision adjustment when approaching a lighted area is not impacted greatly and therefore requires no special consideration.

11.Rapid changes in levels of illumination may be compensated by using transition lighting or adaptation techniques. When transition lighting is provided the roadway sector requiring transition lighting should be illuminated so as to allow the motorist’s eyes to adjust to a different level of illumination. A practical formula for calculating the required roadway length for transition lighting is as follows:

L= (S)( C )(T)

Where, L = Length of Transition Lighting

S = Speed Along Roadway Section in MPH (design speed)

C = 1.47 (Converts MPH to feet per Second)

T = 15 Sec. (Recommended exposure time to allow motorist’s eyes to adjust to different level of illumination).

3.4 TRANSITION LIGHTING

When developing lighting plans, the effects of lighting on the driver’s eye must be understood. According to the “Roadway Lighting Handbook”, a driver’s eye adjusts every time it experiences a lighting change. It is more difficult; and takes longer for the eye to adjust from light to dark than conversely. With this in mind, the handbook specifies that a transition lighting section be provided when moving from one light level to another.

The Illumination Engineering Society recommends that the light level be reduced by no more than 50% in a section of roadway that a vehicle travels along in a 15-second period. This means a driver traveling along the roadway would experience no more than a 50% drop in illumination in 15 seconds. This rationale will be considered when going from any type of zone in Arlington, like going from a commercial area along a residential street into an intermediate or a low-density area. This insures there is uniformity, and does not compromise this design imperative.

From a NJ Turnpike Engineer

The Turnpike has used transitional lighting for many years at our underdeck locations (some classified as “tunnels”), plaza ramps and plazas themselves. Here is a general overview.

AASHTO and IES (Illumination Engineering Society) have guidelines for lighting that our designers follow depending on the road speed and configuration (ramps, gores, underpasses, tunnels, etc.) For example, during daylight hours, the portals of underdeck lighting are brighter than the lighting directly under the structure, as can be observed by an increase of luminaires in the portals. The luminaires are spaced wider as you travel further into the tunnel so as to “transition” the intensity of light, to allow one’s eyes to acclimate to the new environment. Night lighting fixtures will turn on at dusk and the daytime lights are extinguished in stages so as to avoid an abrupt change if someone is in the tunnel during the changeover. Night lighting is at a significantly lower footcandle level than daytime so as not to blind the motorist.

Ramp lighting also has specific “rules” to follow depending on configuration and speed of the merge. Typically we see wattages starting at the plaza of 250 – 400 watts tapering off to 150 watt for the last several poles on an acceleration ramp as a transition zone. Deceleration ramps are the reverse.

The DOT uses many of the same Design Engineers that we retain. They would therefore also have transitional lighting where it is called for by design.

56-2.12 Transition Lighting

Consider step-down transition lighting, or similar visibility measures, for traffic lanes emerging from a lighted area with very high lighting levels. For additional information, consult the ANSI/IESNA RP-8.

http://www.state.tn.us/sos/rules/1680/1680-06/1680-06-01.pdf

13. Transitional lighting should be provided when the average maintained horizontal footcandle level of illumination for lighting designs exceeds 1.00 footcandles. The roadway sector requiring transitional lighting should be illuminated so as to allow the motorist’s eyes to adjust to a different level of illumination and should be traditionally illuminated for no less than 15 seconds. The level of illumination for transitional lighting sector should be equal to approximately one-half of the preceding higher lighted sector.

The terminal illumination in the lowest sector should not be less than 0.25 footcandle nor more than 0.5 footcandle. An expedient formula for calculating the required roadway lengths for transitional lighting is as follows:

L = (RS) (C) (T)

Where L = Length of Transitional Lighting

RS = Running Speed Along Roadway Section in MPH

C = 1.47 (Converts MPH to Feet per Second)

T = 15 See (Recommended exposure time to allow motorist’s eyes to adjust to different level of illumination).

14. Transitional lighting is best provided by maintaining the same average spacing and by using lower wattage lamps. This allows for future extension of the lighting system without having to relocate mountings.

www.visualexpert.com/Resources/nightvision.html

Night Vision

Lastly, adaptation effects have large safety implications. Whenever a person transitions from a brightly lit or very dark environment to one of very different luminance, there will be a large visual loss. Elderly people exhibit impaired abilities and suffer the largest visual loss due to abrupt light changes. Proper design should create smooth transitions from light to dark. For example, building entrances and tunnels now often incorporate a zone of middle light level between the dark night outside and the bright interior lighting. This smoother transition minimizes adaptation effects and permits better vision.