safety engineer expert witness accident prevention reconstruction consulting and analysis OSHA MSHASAFETYBIZ, INC.

Safety Engineering Services

Jay W. Preston, CSP, PE, CMIOSH, President and CEO

Safety Engineer.......Accident Prevention Consulting.......Forensic Safety Engineering.......Accident Investigation.......Accident Reconstruction.......Safety Training.......College Safety Instruction.......Emergency Preparedness.......Safety and  Accident Prevention Expertise and Experience.....Expert Witness......

 German safety engineer  sicherheit ingenieure VDSI arbeitschutz unfall verhutung arbeitsicherheitSpanish seguridad ingeniero safety engineer seguridad de trabajojapan safety engineer japanese anzen accident prevention chuo rodo saigai boshi kyokaiClick:  safety engineer, AQUATIC, swimming safety water safety diving safety pool safety boatingsafety marine and maritime safety construction safety building industry safety site specific safety programs elevator and escalator safety fall safety fall prevention lifelines and lanyards trips slips stumbles falls wheelstops, speed bumps tripping hazards building code compliance defenestration stairway falls balcony falls sidewalk falls walkway falls prevention safety fire safety and fire prevention, automatic sprinklers Glass and architectural glazing safety impact prevention and analysis human factors in accident prevention and safety population stereotypes and expectations industrial safety and accident prevention production machinery safety agricultural safety foodindustry safety plastic and composition material safety woodworking safety metalworking safety rubber industry safety, machine guarding, lock out tag out, OSHA, Cal-Osha manual and mechanical material handling safety and accident prevention forklift safety crane safety conveyor safety Petroleum industry safety drilling rig safety offshore production safety oil industry safety refinery safety playground safety recreational safety hiking and mountaineering safety and accident prevention slip testing slipperiness testing slip and fall accident prevention and safety,tribometry,tribometrist,tribometer motor vehicle and transportation safety and accident prevention trucking safety and accident prevention


Jay W. Preston, CEO

Click for Resumé

Human Factors


I can dig it! bumper sticker

Search for Specifics:

Travel Deals and Discounts for Frugal Jet-setters!

Amazing Travel Packages!

Get YOUR Piece of Travel Action

Hit Counter



Safety Notes for C.A.A.L.A. Convention

I have had the privilege of participating in the CAALA Convention as one of the experts in the "Mock Trial."  My slot was that of "Defense Liability Expert."

This poses a problem, because I believe the model case to be indefensible from a safety engineering standpoint.  I would have advised my client of that fact, and warned him of the consequences of my truthful testimony, should I be called to the stand.

About all I can offer the defense is that the building was built before there were Building Code requirements for level landings on both sides of doors or door swing encroachment requirements.  Therefore, the building grandfathers this requirement, and a decision of negligence per se on this point cannot be sustained.

The owner need only maintain the building to the provisions in force when the building was constructed (for code compliance).  The only exceptions relate to glass shower doors, earthquake protection, and high-rise fire sprinklers.  Frequently juries believe that mere code compliance relieves an owner of any further duty for safety.

The low lighting issue in the City of Los Angeles IS negligence per se because the one footcandle requirement is in the Electric Code and the Fire Code that has no grandfathering.

Here are several salient points that render the installation unsafe and the owners negligent for the condition.

The one-step at the doorway is wrong and unsafe.  It is unexpected, difficult to discern visually, unnecessary structurally, and visually confusing due to cracks and colors (see One-Step information below).

The door swing outward is necessary due to the nature of the occupancy. Requirements for doors not swinging beyond the building line came in after construction.  

It has no stairway safety features.  It is not a stairway by definition under the Building codes.

It is dimly lit (see Lighting information below), reported as .30 footcandles. This is, however, above some code values for entertainment venues, but the show was over at time of incident.  One normally expects low light levels in bars.  

The sign on the door warning of the step down would be easily lost in the clutter of interior decor.  It was not a standard warning sign.

There are plenty of visual cues that show the step.  These are the threshold, the line of the step nose, the line of the blocks where they meet the sidewalk, and a crack in the step.  All are parallel with the actual step nose, and they add to confusion about what really is the step nose. 

One could expect ladies to be in high heels upon exit.

One could expect patrons leaving to be conversing as they did so.

One could expect some degree of motor and mental impairment from alcohol to those exiting, even though the model victim had 1-2 drinks at the bar.


The primary reason to evaluate one-step hazards and accidents is to determine whether or not there is some defect that renders it dangerous and that caused an accident event. The information developed can be used to improve the area to prevent future accidents.

One-step or single step hazards are not generally encompassed by the definition of stairway (two or more risers with appurtenant treads). However, the hazards are essentially the same. The hazard is magnified by the absence of visual cues of the existence of a level change. One-steps are often used only for aesthetics in places where they can be unexpected. Conversation pits are "the pits", and sunken living rooms should be "sunk."

Where there is difficulty in discriminating a step nose due to inadequate light, a likelihood of sensory impairment in surface users, or a confusing surface pattern or coloration, or other irregularity, good practice demands highlighting the steps with delineation stripes or similar treatment applied to the nose edge. To avoid giving users a false cue, the stripes must extend to the edge of the nose. If they stop short of the edges, users will tend to identify the edges of the stripes as level edges, lose their balance, and fall.

Surface users may be caught unaware by an unusual physical feature such as an unnecessary step in a walkway area. In such a location contrasting colors of floor surface, nose delineator stripes, and even a physical barrier such as a railing, may be required to provide a satisfactory degree of safety.

Accident investigations and analysis show that the overwhelming majority of falls occur in transition from flat to inclined modes of travel, from inclined to flat, and at level changes. Accident statistics also show that the first two and last two steps of stairways have the most frequent accidents. A single step tends to combine the zone of transition at both ends into one hazardous area.

The popular press also recognizes the hazards associated with single step hazards. One example appears in the April 1985 New Shelter Magazine: "It is never a good idea to use a single step between two levels of decking--the difference in levels is so slight it can be hazardous. Better to have a minimum of three, 6-inch risers for each level change."

Often a one-step will have a riser that is too low to comply with the building code stairway riser minimum height. Sometimes a linear shadow line will make the step disappear. Patterns in a floor covering can also disguise the true edge of the step.

Single steps are particularly dangerous for several reasons beyond those associated with stairways. The difference in level between the upper and lower landing may be insufficient to provide visual discrimination of the drop. Color changes at the step are frequently ignored by floor covering installers. The single step will not be treated as a stairway with the associated visual cues, railings, or warnings. Regular users or the custodians of the one-step may not consider it sufficiently dangerous to require a warning. Finally, a single step may be placed in a location where there is little or no structural necessity for it.


A major concern on any walking surface is to have sufficient illumination to be able to differentiate level changes, obstacles, and defects. Lighting should be direct and with sufficient contrast to provide adequate visual discrimination to see obstacles.

Visual stimuli are dependent on a number of measurable factors for perception. These elements can be measured, quantified, and evaluated to determine a probability of a specific object being seen by an observer. The elements are:

1. Object luminance (the light returned from the object to the viewer)

2. Background luminance (the light returned from the field surrounding the object)

3. Spectral distribution (Color of object and background)

4. Contrast (Relative luminance difference between object and background)

5. Size of object

6. Duration (Exposure time)

7. Temporal frequency characteristics (Changes with time or rate of flashing)

8. Location relative to line of sight

9. Movement in visual field

10. Variations in luminance of object and background

When the elements in the visual field do not produce their own light, an evaluation of luminance can be derived from the illuminance level or the light falling on the surfaces.

The Illuminating Engineering Society has promulgated standards for safety illumination. The basic standard is given as Figure 2-26 from the IES Lighting Handbook, Application Volume. This is reprinted below. The IES states, "Fig. 2-26 has been developed to list illuminance levels regarded as absolute minimums for safety alone. To assure these values are maintained, higher initial levels must be provided as required by the maintenance conditions."

Fig. 2-26. Illuminance Levels for Safety*

Hazards Requiring Visual Detection:

                          Slight                         High

Normal Activity Level:

                      Low     High             Low     High

Illuminance Levels:

Lux                 5.4         11             22         54

Footcandles  0.5            1              2            5

*Minimum illuminance for safety of people, absolute minimum at any time and at any location on any plane where safety is related to seeing conditions.

>Special conditions may require different illuminance levels. In some cases higher levels may be required as for example where security is a factor. In some other cases greatly reduced levels, involving total darkness, may be necessary, specifically in situations involving manufacturing, handling, use, or processing of light-sensitive materials (notably in connection with photographic products). in these situations alternate methods of insuring safe operations must be relied upon.

Note: See specific application reports of the IES for guidelines to minimum illuminances for safety by area.

Given the nature of the hazard, the IES minimum illuminance level should be at least 2.0 footcandles.

IES recommended illuminance levels include 20 footcandles for corridors and active storage rooms, 1 footcandle for garden paths, 0.9 footcandles for roadside sidewalks in commercial areas, and 0.5 footcandles for park walkways. These are, of course, minimum standards and may be much less than required in an environment frequented by specific populations. Pedestrian security in general parking areas and related walkways requires illuminance levels of 4 footcandles. Many building codes, including recent UBC, recognize the minimum of 1 footcandle for all exit lighting. The Los Angeles Municipal Fire Code and Electric Code requires one footcandle for exit hallways, stairways, and corridors.  Recent additions to the Los Angeles Municipal Building Code now incorporate the one footcandle requirement.

Hit Counter 

Copyright 2000 - 2011, Jay W. Preston.  Distribution permission granted when this notice is printed in full.  For questions or comments: contact  The J-P, Plus Design and SAFETYBIZ. are registered service marks of Jay William Preston. Permission for use of specific Safety Subject Information is only granted when this notice is printed in full and Preston has been contacted by phone, fax, or email prior to use.