Corso di Sistemi di Trazione Lezione 8 Ergonomia

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

Sfondo 4 Visibilità del conducente 3 2 1 4 3 2 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 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 Emotion Reaction (volition) What is it? A deer 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 3 x 10 -4 e 10 x 10 -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 Time Cumulative Time (sec) 0. 31 Eye movement 0. 09 0. 40 Fixation 0. 20 1, 00 Recognition 0. 50 1. 50 2) Initiating brake application 1. 24 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 Paretina 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 accettabile Accelerazione e dec. m/s 2 Longitudinale 1, 0 2, 0 4, 0 Componente orizzontale 0, 8 1, 5 3, 0 Componente verticale 0, 2 1, 0 2, 0 Contraccolpo m/s 3 0, 6 1, 0 1, 5

Ambiente interno confort Non accettabile 20 – 22 12 – 35 < 12 > 35 Umidità (%) 50 < 30 > 70 Ventilazione m 3/h-pass 35 < 20 <8 Rumore d. BA < 65 75 – 85 > 85 Vibrazioni mm/s 0, 2 1, 2 3, 0 Temperatura (°C)

Spazio confort Densità (pass/m 2) Umidità (%) Ventilazione m 3/h-pass Non confort accettabile 2– 3 >3 >6 15 – 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 F 104 A Cause: Bad Seat Design F 105 D “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. 6 1. 1 0. 9

Sistema U-M Segnali video Decisioni Percettori Processo Attuatori 68

Driver task analysis in real time

Le informazioni nel sistema U-M MACCHINA ACCUMULO INFORMAZIONI INGRESS O PERCEZI ONE ELABORA ZIONE E DECISIONE AZION E UOMO ACCUMULO INFORMAZIONI ELABORA PERCEZI AZIONE E DECISION E ACCUMULO INFORMAZIONI CONTRO LLO PROCES SO USCITA

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

Two functions lateral control longitudinal control

Cruising and collision avoidance