POSTECH H uman S ystem D esign Lab oratory Serious stair injuries can be prevented by improved stair design Michael S. Roys (2001) Applied Ergonomics Thu. Kim, Hee-jin

POSTECH H uman S ystem D esign Lab oratory Contents 1.Introduction 2.Types of stair accident 3.Stair terminology and geometry 4.The stair gait 5.Hazards associated with the stair gait 6.Can these injuries be prevented? 7.The costs and the benefits 2

POSTECH H uman S ystem D esign Lab oratory 1. Introduction  Stairs are the most dangerous component of any home  Home accidents: an estimated 2.5 million injuries, and a further 4000 deaths in the UK(Consumer Safety Unit DTI, 1997)  About 230,000 of these injuries and 497 deaths resulted from falls on stairs  Home accidents of the Korean aged: 428 accidents ( 한국소비자보호원, 2003)  안전사고 발생 장소  This paper  Checks basic things of stair and stair accidents  Considers what could be done to reduce the number of accidents 3

POSTECH H uman S ystem D esign Lab oratory 2. Types of stair accident  Major reasons for stair accidents  User behavior Difficult to control Will probably always be with us Ex) Tripping over objects, Running up or down the stairs, Missing steps, Taking two or three steps at a time, Momentary lack of attention  Maintenance Easier to control Is necessary to prevent the deterioration of the stair condition Ex) Broken treads, Loose carpets or any other component  Design Good design could prevent some types of accidents from ever occurring Ex) Poor design: large gaps in a balustrade( 난간 )  falling 4 Fundamental accident reason that can be controlled  should be studied Can be solved by accident reduction programmes (ex. Safety campigns)

POSTECH H uman S ystem D esign Lab oratory 3. Stair terminology and geometry  Stair geometry 5 the vertical distance between two consecutive treads British Standards give guidance on acceptable rise sizes so that the climb is not too excessive or the steps so low(100mm~220mm) The horizontal distance between two consecutive nosings between 220 and 350 mm The angle between a line joining consecutive nosings and the horizontal Tread ↓ Nosing( 계단코 ): The part of the tread that overlaps the tread below British Standards - maximum pitch: 42 ∘ - G+2R: 550~700mm

POSTECH H uman S ystem D esign Lab oratory 3. Stair terminology and geometry  Acceptable stairs based on the relationship between rise and going 6 British Standards - maximum pitch: 42 ∘ - G+2R: 550~700mm

POSTECH H uman S ystem D esign Lab oratory  Description of the normal stair gait(Templer, 1992) 4. The stair gait 7 Swing phase - The leading foot swings over two nosings(of the tread the leading foot was on and the tread the rear foot is now on) and stops over the tread below Stance phase - As this leading foot starts its descent, the heel of the rear foot begins to rise, leaving the weight of the body supported on the metatarsal heads of the rear foot In descent

POSTECH H uman S ystem D esign Lab oratory  Description of the normal stair gait(Templer, 1992) 4. The stair gait 8 Stance phase - The rear foot begins to rise up onto tiptoe to help lift the whole body upwards and forwards Swing phase - Simultaneously, the rear leg swings past the forward foot over two nosings onto the step above  Differences between stair gait pattern & walking on the level  Each step initiates on the toes and ball of the foot rather than the heel  The vertical transfer of weight requires either extra effort in ascent or a controlled fall in descent In ascent

POSTECH H uman S ystem D esign Lab oratory 5. Hazards associated with the stair gait  On ascent The accidents tend to be less severe in nature (Templer, 1992) ( ∵ ) The center of gravity is slightly forward  most falls are relatively small & towards the higher steps  The risky situation on ascent  The greatest risks are during the swing phase High possibility of tripping  When the user is pushing off the lower tread with the rear foot High possibility of the foot slipping (if the slip-resistance of the tread is low)  When the user completely misjudge the position of the next tread High possibility of slip off 9

POSTECH H uman S ystem D esign Lab oratory 5. Hazards associated with the stair gait  On descent The accidents tend to result in more serious injuries (Templer, 1992) ( ∵ ) A fall here could cause the user to descend the full fight, hitting any number of the steps on route  can cause broken bone or head injuries  The risky situation on descent  When “the going of the treads” < “the shod foot of the user” Missing the next treads The going decrease in size ↓  The problems are exaggerated 10 Our interest!

POSTECH H uman S ystem D esign Lab oratory 6. Can these injuries be prevented?  Accidents(  injuries) prevention Make the stair goings larger than the feet of the user Guidelines* about minimum goings size by considering average foot length(Pheasant, 1988) - 280mm for public(crowed) stairs - 250mm for semi-public(libraries) stairs - 220mm for private stairs The anthropometric data is too old to reflect present trend  correction is needed Ex) Public stairs  300mm (99% females and 50% males with 30mm shoe allowance) Semi-public stairs  270mm (50% females and 2% males with 30mm shoe allowance) Private stairs  245mm (2% females and 1% males with 30mm shoe allowance) 11 Department of the Environment and the Welsh Office, 1992 British Standards Institute, 1984  This change takes a large number of years to cover all building in UK  And by that time, the population will probably be even larger anthropometrically  Begin now!!

POSTECH H uman S ystem D esign Lab oratory 7. The costs and the benefits 12 CostSaving ￡ 40(8 만원 ) for “220mm  245mm” 180,000 new homes per year 5% prevention of stair accident would prevent another 500 accidents & at least 1 death per year  Can save ￡ 5 million(100 억 ) per following year