Vehicle Motion Human Factors

Homework Chapter 2: #3, 6, 7

Human Factors Rational Design of goods and services for people Primary human requirements increased speed increased range increased capacity Secondary safety, comfort & convenience, status

Environment Where workspace is located effects person’s performance lighting, noise, vibration, climate, pollutants Man - Machine - Environment interaction want to optimize

Human Variation Design is based on 90% of people Top and bottom 5% not in design who’s not included? Adaptation & Instruction want to limit instructions How is a car laid out? Where are the important components Commonality

Human Contact Physical, Physiological, Biochemical Size Reach Strength Body Composition Perception - Reaction P-R, Info Processing, Motor Performance Cognitive and Social

Pedestrians Important piece of urban design Crosswalk placement Social distance Personal distance Intimate distance

Pedestrians How does personal space change ? Transit airplanes waiting areas cars

How big is a pedestrian?

Visual Acuity Contrast, brightness, illumination, relative motion Acuity decreases with increased visual angle

Perception Reaction Time Time from stimulus to response Depends on complexity of info P-R 0.5 - 2.5 seconds depending on event type Wake Up

Fig 2.2 pg 22 P-R times Expectancy Continuity – experiences of the immediate past are expected to continue Event – Events that have not happened previously will not happen Temporal – for cyclic events the longer a given state is observed the more likely it will change

Distance covered during P-R time Pedestrians 1.47Vt Pedestrians ~ 3.5fps, elderly pop ~3.0 fps just changed Table 2.3 DWI - Figure 2.3

Lateral Displacement Driver moves away from objects on the side of the road Want to maintain a comfort zone between car and objects

Lateral Displacement Closer objects is to pavement edge the more lateral displacement 3.3 ft for 8 ft lane 1.8 ft for 12 ft lane Can estimate lateral displacement need l, v, dQ/dt

Lateral Displacement Critical rate of change in visual angle if dQ/dt is less than critical assume collision l = a cotQ dl/dt = -acsc^2QdQ/dt dQ/dt = va/(a^2+l^2)

Lateral Displacement A vehicle traveling 40 mph was observed to displace laterally when it was 300 feet from a bridge abutment placed 6 feet to the right of the path. At what longitudinal distance from the same abutment would you expect the same driver to displace laterally when traveling 60 mph?

Lateral Displacement What is critical rate of change (dQ/dt) dQ/dt = {(40*1.47)*6}/(6^2 + 300^2) = 0.0039rad/sec For 60mph 0.0039 = {(60*1.47)*6}/(6^2 + L^2) L = 368 feet

Forces Acting on a Vehicle Propulsive (M) Resistance (R) Centrifugal (C) Weight (T) ma Supporting Forces (S)

Resistance Inherent Grade Curvature vehicle is moving through something R is a function of T and V Grade adds resistance or increases speed Curvature from centrifugal force can be eliminated w/ banked curves

Grade

Curvature

Vehicle Motion Superelevation e is the amount of banking in ft/ft on a curve e + f = v2/gr depends on speed Table 2.4 – Values for f to negate f (no hands) e = v2/gr v in fps e= v2 /15R v in mph

Vehicle Motion v=dx/dt a = dv/dt a=(dv/dx)v vdv = adx v =at + v0 x = v0t +1/2(at2)

Braking Distance Db= (v2-v02)/2g(f+G) f = 11.2fps^2/32.2 = 0.348 used for design Not Brake type dependent – why? NOT Weight dependent - why? Does not account for reaction time

Safe Stopping Distance Time to perceive and respond + time to brake to a stop P-R time =2.5s want to be conservative SSD = 1.47V(2.5) + (v2-v02)/2g(f+G)

Decision Sight Distance Time to perceive and respond + time to brake to a stop P-R time =2.5s want to be conservative SSD = 1.47V(decision time) + (v2-v02)/2g(f+G)

Example How long does it take a vehicle to brake to a stop from 60 mph On a 5% downgrade On a 5% up grade On ice on a 5% upgrade

Dilemma Zones Area around intersection - can’t stop can’t go –occurs when Yellow time is too short Need proper Y P-R time

Dilemma Zones a2 is comfortable deceleration rate 4- 5 fps standing 8 -10 fps seated xo > xc no problem xo <= xc dilemma Cannot cross intersection in Y+AR

Dilemma Zones Can find minimum amber needed to eliminate dilemma zone Amber should be not more than 5 seconds Amber time = D/1.47V Assume 1s P-R time for signal

Dilemma Zones How long should the amber interval be for the following: Design Speed = 35mph Intersection = 30 feet wide Vehicle length = 15 feet P-R time = 1 s Stopping distance = 1.47*35*1 + (35^2-0^2)/[30(0.0348)] = 169 feet Amber = 169/(1.47*35) = 3.28s

Dilemma Zones How long should the amber interval be for the following: Design Speed = 35mph Intersection = 30 feet wide Vehicle length = 15 feet P-R time = 1 s Distance thru intersection= 168+30+15 = 213 ft Amber = 213/(1.47*35) = 4.13s can use 3.28s Y + 1s AR