Last updated July 28, 1997
Archive
Previous tutorial: Quality Creation
Return to TRIZ Page (home page)
List of problems
Letīs consider the future of a modern city. First, list of problems:
City for cars, city for pedestrians.
We select the pair "city for cars only, city for pedestrians only". Which contradictions
we meet?
I myself live in Turku, which is a relatively small city (160 000 inhabitants) in the
southwest corner of Finland. Some time ago one street in the city was turned to a so
called street for public transport. The sidewalks were made broader, the middle of street
reserved fur buses only, and individual cars excluded. A street became more
convenient for buses, and, maybe, for pedestrians, but at the same time new restraints on
the liberty of drivers appeared. If, in contrary, sidewalks are curtailed, the life will be a little
more easy to drivers, but pedestrians will protest. The problem remains. Both compromises
are unsatisfactory. Too little room for pedestrians, too little room for cars.
Increasing the difference between common alternatives we get two opposite systems.
First: a city only for cars, walking on the streets is prohibited. Second: city only for
pedestrians, cars are prohibited.
No we have two known systems with "opposite" pluses and minuses. We describe the
features of the systems by the two pluses matrix:
| System | Ease of driving | Ease of walking |
| City for cars only | + drivers happy | - pedestrians angry |
| City for pedestrians only | - drivers angry | + pedestrians happy |
Engineering Contradiction. The engineering contradiction is a situation
when improving
of one feature of the system (product/process) leads to undesirable worsening of another.
A city good for cars is bad for pedestrians and vice versa. "Plus" is coupled with "minus".
Ideal Final Result. The ideal final result is a system which have the both
pluses and none
of the minuses of the initial prototypes. We can directly write the features of a solution:
+ drivers are happy
+ pedestrians are happy
We complete our table:
| System | Ease of driving | Ease of walking |
| City for cars only | + drivers happy | - pedestrians angry |
| City for pedestrians only | - drivers angry | + pedestrians happy |
| Ideal final result | + drivers happy | + pedestrians happy |
Physical contradiction. If we consider more carefully our examples we
see that we
are dealing not only with alternative, but with opposite systems. If we make a sidewalk more
broad, weīll have less room for cars. If we continue to make a sidewalk more and more
broad, no room will remain for cars, we get a street for pedestrians only. Analogously, we
can give more room for cars so that the sidewalk disappears and weīll have the street for
cars only. So the breadth of sidewalk should be for example 30 meters (whole street is
sidewalk) and at the same time the breadth should be zero (a street only for cars). Letīs
make our matrix:
| System | Ease of driving | Ease of walking |
| Sidewalk 0 m | + drivers happy | - pedestrians angry |
| Sidewalk 30 m | - drivers angry | + pedestrians happy |
The matrix contains actually not one, but two contradictions. Engineering contradictions
are conflicts between two different variables or requirements. Improving the parameter
"ease of driving" we worsen the other parameter "ease of walking". Or increasing
carrying capacity and speed we worsen or increase fuel consumption, which is physically
a totally different variable. The conflict: abroad sidewalk - a narrow sidewalk, or the conflict:
a very broad sidewalk - a sidewalk with zero breadth, means that the same variable
should have different, incompatible values.
Space, time and structure. Separation in space is the first way to
resolve
a physical contradiction. A two story city separates contradictory properties in
space: in a floor for cars the breadth of a sidewalk is zero, in a floor pedestrians 30 m or
more. Traffic lights separate the properties in time: at one time whole street serves
only cars, at another time only pedestrians.
If we can not separate properties in space, nor in time, we can separate them in structure.
Separation in structure means that the parts of the system and the system as whole have
opposite features. An escalator consists of rigid and unflexible parts (steps). As whole
the escalator is a flexible system.
It is interesting to use the escalator as an analogy and try to figure the solution of our
transport problem. Horizontal escalators or small "moving roads" are existing technology,
in airports, for example. We can make a moving street, which can carry passangers and
cargo, or deliver functions of a car. The moving street works as a a car and at the same time
people can walk on it.
One can say that a chain of associations is a little bit artificial. I agree. Letīs correct the
model, or matrix. We need movable vehicles, for instance cars. At the same time we need
an immovable street for pedestrians. The two systems are a movable vehicle and an
immovable street:
| System | Ease of driving | Ease of walking |
| Movable vehicle | + drivers happy | - pedestrians angry |
| Immovable surface | - drivers angry | + pedestrians happy |
| Moving road | + drivers happy | + pedestrians happy |
A moving road separates contradictory properties in structure. The "belt" is moving, the system as
whole is immovable.
It is important to note that the problem changes during the solution process. In the beginning the
problem was a conflict between a car and a pedestrian. At last we got the problem how to combine
the features of movable and immovable systems. The statement and solving of problems is an
iteration process.
How ideal is a two story city? Letīs compare the idea of two story
city with
general requirements of the IFR:
No system as an alternative
Letīs reformulate our transport problem using the "no system" as an alternative:
| System | Transport capacity | Ease of use |
| Usual street | + much transport | - conflict |
| No street | - no transport | + no conflict |
The ideal street is "no street", which still supports cars and pedestrians. The function of the
removed street should be transferred to other systems. Highways, tunnels, buildings, roads
for pedestrians, and so on can deliver the functions of a street.
| System | Transport capacity | Ease of use |
| Usual street | + much transport | - conflict |
| No street | - no transport | + no conflict |
| Other components | + much transport | + no conflict |
We build "Domb`s table":
| Function Statement, Analysis and Trimming | |||||
|---|---|---|---|---|---|
| A function carrier | Does this to | B object of function | Useful/ harmful |
Is the function necessary? | Could B do it? Some other element? |
| Car on usual street | moves | people | + | Yes | Car in tunnel/ on highway |
| Car on usual street | moves | cargo | + | Yes | Car in tunnel/ on highway |
| Car on usual street | impacts | pedestrian | - | No | |
| Usual street | supports | pedestrian | + | Yes | Pedestrian street |
| Usual street | supports | car | + | Yes | Tunnel/ highway |
Evolution trends of a street. By development lines we can
get suppositions
how the system can evolve. A street is a solid monolith. A liquid street? A street from gas?
Maybe air cushion as street?
Rhythms coordination: a vibrating street? Resonance which allows to eliminate noise?
Continuously vibrating street which moves vehicles?
Improving ideas. Often the evolution trends give interesting,
but rather
exotic ideas. For example "liquid street". A canal is one kind of liquid street. We can consider
the idea we derive from trends as an alternative system, which has its pluses and minuses.
"A liquid street" is absolutely durable, but difficult to use. Maybe we can find or invent a
solid substance which recovers itself as liquid and donīt require maintenance.
Updated July 28, 1997
Archive
Previous tutorial: Quality Creation
Return to TRIZ Page (home page)