Transcript Introduction to Transportation: Lecture 3
Corso di Sistemi di Trazione Lezione 8: Ergonomia del conducente e dei passeggeri Lezione presentata dal Prof. F.Filippi
A. Alessandrini – F. Cignini – C. Holguin – D. Stam AA 2014-2015
Definizioni di Ergonomia
"Ergonomics (or Human Factors) is the scientific discipline concerned with the understanding of the interactions among human and other elements of a system, and the profession that applies theory, principles, data and methods to design in order to optimize human well-being and overall system performance" International Ergonomics Association (IEA).
Origine dell’ergonomia
Durante la II guerra mondiale era necessario semplificare i comandi degli aerei per avere un gran numero di piloti con pochi giorni di formazione.
Successivamente l’ergonomia è servita a migliorare la vita del lavoratore, l'efficienza e l'affidabilità dei sistemi uomo-macchina. L'obiettivo attuale è progettare oggetti, servizi, ambienti di vita e di lavoro, nel rispetto dei limiti dell'uomo, per migliorarne il benessere e aumentarne le capacità.
The driving tasks
It can be complex and demanding on the driver. For example, driving on an unfamiliar interstate highway or having to take a detour due to an accident. Driving errors occur when the driver experiences task overload or when the driver ’ s expectations are not met. For example, a left hand off-ramp on an interstate when the majority of off-ramps are on the right side. Providing sufficient information to the driver in a timely fashion can help prevent driving errors.
The three levels of the driving task Control: Includes basic steering and speed control.
Guidance: Includes road-following, car-following, overtaking and passing, merging, lane changing and responding to traffic control devices, obstacle detection.
Navigation: Includes trip planning and route following.
Performance of the driver impacts the following design parameters Sight passing distances Lane widths Location of traffic control devices Speed limits Traffic signal timing Stopping sight distances Roadside safety features
Components of Highway Mode
Need to understand the limitations and interactions between • Driver • Pedestrian • Vehicle – Heavy trucks – Passenger vehicles – buses – Bike (but may have separate facilities) • Road
Design Driver
Wide range of system users • Ages: 16 year old to 80 year old • Different mental and physical states • Physical (sight, hearing, etc) • Experience
Performance of the driver impact the following design parameters Sight passing distances Lane widths Location of traffic control devices Speed limits Traffic signal timing Stopping sight distances Roadside safety features
Components of Highway Mode
Understand the limitations and interactions: Driver Pedestrian • • • • Vehicle Heavy trucks Passenger vehicles buses Bike (but may have separate facilities) Road
Human Characteristics
Perception – Reaction Time Visual Reception Walking Speed Hearing Perception Actions taken by drivers depend on their ability to receive, evaluate, and respond to situations ( Ex.: dog darting into roadway)
Wide range of system users
Ages: 16 year old to 80 year old Different mental and physical states Physical (sight, hearing, etc) experience
La variabile tempo
Il sistema U-M-A deve considerare: • Il tempo reale dell’uomo che opera con le macchine in un determinato ambiente • Il tempo delle prossime ore in cui subentrano fenomeni di adattamento e stanchezza • Il tempo lungo degli anni in cui si manifestano fenomeni di obsolescenza professionale, diminuzione delle capacità, stanchezza dovuta alla routine.
Human performance in traffic
The fundamental parameters in human performance are largely centred around neuromuscular and cognitive time lags.
These are perception – reaction time, control movement time, responses to the presentation of traffic control devices, responses to the movements of other vehicles and to hazards in the roadway.
They are related to the different segments of the driving population.
Visual reception (acuity)
Static (stationary objects): • Depends on brightness • Increases with increasing brightness up to ~ 3 candles (cd/sq ft) and remains constant after that • Contrast • Time (0.5 to 1.0 second) Dynamic (ability to detect moving objects) • Clear vision within a conical angle 3° to 5° • Fairly clear within 10° to 12°
Peripheral Vision
Ability to see objects beyond the cone of clearest vision (160 °): • Age dependent • Objects seen but details and color are not clear
Cone of Vision
Impegno spaziale del conducente La forma e l’estensione della zona rigata di impegno spaziale del conducente è funzione della velocità, raggio di curvatura e distanza di frenatura e interagisce con il tempo di reazione.
1 secondo 2 secondi 3 secondi
1 Sfondo 3 2 4 Visibilità del conducente 3 2 4 1 Autostrada v = 100 km/h 1.
Zona di illeggibilità, moti di traslazione 2.
Campo di visibilità periferica, moti apparenti di rotazione e traslazione 3. Cono di concentrazione dell’attenzione, campo statico 4. Sfondo, macroelementi del paesaggio
Color Vision
Ability to differentiate one color from another • Lack of ability = color blindness • Combinations to which the eye is the most sensitive – Black and white – Black and yellow
Vision
20/20 can read 1/3 inch letters at 20'
Example:
a driver with 20/20 vision can see a sign from a distance of 90 feet if the letter size in 2 inches. How close would a person with 20/50 vision have to be to see the same sign?
X = (90 feet) * (20/50) = 36 feet
How large would the lettering have to be for a person with 20/60 vision to see the same sign from 90 feet?
h = 2 inches (60/20) = 6 inches
Glare Vision
Glare Vision results in a decrease in ability for a driver to see and causes discomfort for the driver.
Glare Recovery is the time it takes for a driver to recover from the effects of glare after passing a light source.
Research has shown that the time to recover from dark to light conditions is 3 seconds and 6 seconds to recover from light to dark conditions. Glare Vision is a problem for older people who drive at night.
Glare effects can be minimized by reducing the brightness of lights and positioning lights further from the roadway and increasing the height of the lights.
Glare Recovery
Ability to recover from the effects of glare • Dark to light : 3 seconds - headlights in the eye • Light to dark: 6 seconds – turning lights off • Usually a concern for night driving
Need to provide light transitions
Aging’s impact of vision
Older persons experience low light level – Rules of thumb – after 50 the light you can see halves with each 10 years Glare – overloading eye with light – Older drivers can take twice as long to recover from glare Poor discrimination of color Poor contrast sensitivity
Depth perception
Ability to estimate speed and distance • Passing on two-lane roads • Judging gaps • Signs are standardized to aid in perceiving distance Very young and old have trouble judging gap
Perception-Reaction Process
Perception Identification What is it? A deer Emotion Reaction (volition) Better stop!
Typical Perception-reaction Time (PRT) range 0,5 to 7 s
Perception-Reaction Process
4 stages: Perception – Sees or hears situation (sees deer) Identification – Identify situation (realizes deer is in road) Emotion – Decides on course of action (swerve, stop, change lanes, etc) Reaction (volition) – Acts (time to start events in motion but not actually do action)
Foot begins to hit brake, not actual deceleration
Perception-Reaction Process
Perception: • Seeing a stimulus along with other perceived objects.
• Out of the corner of your eye you see something coming out of the woods towards you.
Identification: • Identification and understanding of the stimulus. Alternatives are developed.
• You realize that it is a deer about to cross the highway in front of you. Do you swerve to miss it? Can you stop in time to miss it? Do you speed up to miss it?
Emotion: • Judgment is made as to the proper course of action. A decision is made.
• You decide the best course of action is to swerve and hopefully miss it.
Volition: • Reaction or execution of decision
PRT
Determined from research: • 0.5 seconds to 0.75 seconds for most driving tasks.
• 0.5 seconds up to 4 .0 seconds for complex driving tasks.
PIEV times are dependent upon the driver’s rest, influence of alcohol and/or drugs.
AASHTO Design values: • 2.5 seconds for computing stopping sight distances.
• 2.0 seconds for intersection sight distance due to the “degree of anticipation” of the driver approaching an intersection.
Driver's braking response
Prior to the actual braking of the vehicle there are two steps: 1. the perception-reaction time (PRT); 2. the movement time (
MT
), immediately following.
Response to the vehicle ahead
The rate of change of visual angle triggers a warning that an object is going to collide. Human visual perception of acceleration of an object in motion is very gross and inaccurate.
It is very difficult for a driver to discriminate acceleration from constant velocity unless the object is observed for 10 or 15 sec. The major cue is rate of change in visual angle with thresholds normally distributed between 3x10 -4 e 10x10 -4 radians/sec.
Lognormal Distribution of P-R Time Probability density function The log-normal probability density function is widely used in quality control engineering and other applications in which values of the observed variable,
t
, are constrained to values equal to or greater than zero, but may take on extreme positive values, exactly the situation that obtains in considering P-R time.
PRT
Chaining Model of PRT
Component 1) Perception latency Eye movement Fixation Recognition Time (sec) Cumulative Time (sec) 0.31
0.09
0.20
0.50
2) Initiating brake application 1.24
0.31
0.40
1,00 1.50
2.74
The PRT Factors
Environment: • Urban vs. Rural • Night vs. Day • Wet vs. Dry Age Physical Condition: • Fatigue • Drugs/Alcohol
PRT Factors
medical condition visual acuity ability to see (
lighting conditions, presence of fog, snow, etc
) complexity of situation (
more complex = more time
) complexity of necessary response expected versus unexpected situation (
traffic light turning red vs. dog darting into road
)
Aspettativa e tempo di reazione
Il ruolo dell’aspettativa è fondamentale per la comprensione del comportamento del conducente.
Es. il tempo di giallo ai semafori Esperimenti sul tempo di reazione per frenare nel caso di situazione improvvisa (A) e con avviso (B).
A) mediana 0,73 s variabile tra 0,5 – 1,1 s B) 0,54 0,4 – 0,8
Blood Alcohol Concentrations BAC
Driver Impairment at Various BACs DAT (Divided Attention Test) Raw Scores, all subjects (N = 168)
How are these factored into design?
Design criteria must be based on the capabilities and limitations of 1) Best drivers 2) Average driver 3) Worst drivers
Il posto di guida
Area di ottima acuità visiva
Area di ottima acuità visiva
Visibilità dei controlli e display
Area entro cui i display principali devono essere collocati
Posizioni raccomandate dei segnali di allerta visivi
Area di normale e massima presa
Esempio di tre display elettronici per la velocità
Circolare Orizzontale e verticale Digitale
Posture di conducenti
A e B sono una cattiva postura con affaticamento del disco.
C è la postura buona con il peso distribuito uniformemente.
Forme variabili del supporto lombare determinate dalla camera A, B e C
Progetto di postura per autista bus
trasparente Coni di visibilità a sedile tutto indietro 51
Sezione
52
Comfort nei mezzi di trasporto collettivo Fattori del comfort: • Aspetti dinamici • Ambiente interno • Spazio
Aspetti dinamici
Passeggero in piedi tenuto confort Non confort Non accettabile Accelerazione e dec. m/s 2 Longitudinale 1,0 2,0 4,0 Componente orizzontale Componente verticale Contraccolpo m/s 3 0,8 0,2 0,6 1,5 1,0 1,0 3,0 2,0 1,5
Ambiente interno
Temperatura ( °C) Umidità (%) Ventilazione m 3 /h-pass Rumore dBA confort Non confort 20 – 22 12 – 35 Non accettabile < 12 > 35 50 35 < 65 < 30 > 70 < 20 75 – 85 < 30 > 70 < 8 > 85 Vibrazioni mm/s 0,2 1,2 3,0
Spazio
Densità (pass/m 2) Umidità (%) Ventilazione m 3 /h-pass confort Non confort 2 – 3 > 3 Non accettabile > 6 15 – 25 > 25 > 200 1 – 2 < 1,0 < 0,2
Human-Capable Design
Creating products that expose users to less mechanical stress in order to: • Decrease risk of operator injury • Increase operator performance (efficiency) • Allow operators to safely and comfortably interact with products longer
System Safety reviews
• Considers risk of injury to human • Tendency to focus on equipment failure conducted during design phase of the product development cycle • Strive to identify and mitigate injury risks
before
products are deployed • Alternative is expensive retro-fits • May not optimize design to avoid features that compromise human performance
Methods & Techniques Employed • Preliminary Hazard Analysis • Failure Mode and Effect Analysis • Fault Tree Analysis • Management Oversight & Risk Tree • Energy Trace and Barrier Analysis
Limitations of Approach
• Struggle to Capture the “Human Side” • System Safety tools dependent upon assessor’s knowledge of human capabilities • Analyses are not structured in a way that obligates users to consider long term effects on human operators • Tend to be “product-oriented” at the expense of the human system component
Common System Design Errors
Dimensional Incompatibility
Sizing • Human-Machine Couplings • Wearables (headgear & clothes) Accesses • doors/hatches & portals Reaches • arms & legs
Example: Access Dimensions Problem Pilots Killed Ejecting From F104A
Cause: Bad Seat Design
F105D “Sample” Cockpit
Example: Poor Workstation Design Shortened muscles compress nerve Excessive Reach Requirement.
Bike Design Causes Headaches.
Detail: Chronic extended neck posturing shortens muscle in back of neck, increases pressure on suboccipital nerve, and may cause headaches & disc disease
Common System Design Errors
Excessive Metabolic Demand
Regional Fatigue Overusing smaller muscles within a specific region of the body Systemic Fatigue Overusing larger muscles from multiple body regions • • Activity stresses heart & lungs Heat stress may contribute to overall metabolic load
System Safety and Human Systems Integration (HSI) Both require risk identification System safety has focused on risks to systems Human Systems Integration focus on design for user
Develop Better Risk Assessment Tools Based on human capability and exposure tolerance limits for these common problem areas: • Excessive Muscular Exertion • Extrinsic External Load • Excessive Metabolic Demand • Dimensional Incompatibility • Extrinsic Mechanical Energy Exposure Design engineers can use them to guide decisions during early product development.
Procurement of Heavy Vehicle
Risk Analysis Reveals Following: • Vehicle operation exposes personnel to whole body vibration • Purchase decision should consider injury risk based upon existing standards
1.1
0.9
Decisioni
Sistema U-M
Segnali video Percettori Processo Attuatori 68
Driver task analysis in real time
Le informazioni nel sistema U-M
INGRESSO MACCHINA ACCUMULO INFORMAZIONI PERCEZIONE ELABORAZIONE E DECISIONE AZIONE CONTROLLO PROCESSO UOMO ACCUMULO INFORMAZIONI PERCEZIONE ELABORAZIONE E DECISIONE AZIONE PROCESSO USCITA ACCUMULO INFORMAZIONI
Confronto Macchina Uomo
La macchina è migliore nel:
• Rispondere con velocità, potenza, precisione • Immagazzinare e richiamare informazioni • Eseguire compiti monotoni il rispetto degli standard • Elaborare le informazioni in modo deduttivo • Cancellare completamente informazioni dalla memoria • Eseguire simultaneamente compiti diversi
L’uomo è migliore nel:
• Riconoscere forme e modelli • Immagazzinare e richiamare informazioni rilevanti • Improvvisare • Ragionare in modo induttivo • Esprimere giudizi di valore
Livelli di automazione nel processo decisionale 1.
L’uomo (U) prende in esame decisioni alternative, sceglie e attua una decisione.
2. Il computer (C) propone un insieme di decisioni alternative, U lo può ignorare nel prendere ed attuare una decisione.
3. C propone un limitato numero di decisioni alternative, U sceglie una di queste.
4. C propone un limitato numero di decisioni alternative e ne suggerisce una, U può accettare o respingere, ma ne sceglie una e la attua.
5. C propone un limitato numero di decisioni alternative e ne suggerisce una che C attuerà se U approva.
Livelli di automazione nel processo decisionale 6.
C prende la decisione e informa U in tempo perché possa fermare l’attuazione.
7. C prende e attua la decisione, informa U, ma successivamente.
8. C prende e attua la decisione, informa successivamente U se richiesto da U.
9. C prende e attua la decisione, informa successivamente U se lo ritiene necessario.
10. C prende e attua la decisione in completa autonomia.
Automated functions on cars
lateral control
Two functions
longitudinal control