tte4004%20Chapter%202%2C3 - Characteristics of the Driver,...

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Unformatted text preview: Characteristics of the Driver, the Characteristics Pedestrian, the Vehicle, and the Road Why understand characteristics and Why quantify them? – Age difference – Gender difference – Mode difference – Environmental difference Characteristics of the Driver, the Characteristics Pedestrian, the Vehicle, and the Road 14% of Drivers in the US are 65 years 14% and older A wide mix of vehicle types and sizes. wide More of SUVs in the fleet mix Road should be designed for strangers Road and accommodate everyone The Human Response Process The Visual Reception: Visual – Visual Acuity Sharpest 3-5 degree, 10-12 is clear Sharpest Optimal time to identify object 0.50-1 sec. Optimal – Peripheral Vision Up to 160 degree angle Up Deteriorates with age especially > 60 Deteriorates – Color Vision (color blindness) Use of shapes Use White and yellow on black for contrast White The Human Response Process… The Continued – Glare Vision and Recovery Night versus tunnel driving Night Sensitivity to glare especially at age Sensitivity of 40 and beyond – Depth Perception Ability to estimate speed and Ability distance Important on two-lane roads Important – Hearing Perception Perception-Reaction Process Perception – Perception and Reaction Time: P.I.E.V. – Perception, Intellection, Emotion, and Volition – db = 1.47*v*t db in feet , v in mph, and t in seconds Brake Reaction Time: Brake AASHTO Recommendations: AASHTO – Stopping Sight Distance: 2.5 seconds – Traffic Signal Change Interval: 1.0 Second Perception-Reaction Time Perception Distance traveled D = vt Distance v=speed in fps v=speed t= 2.5 seconds t= Conversion of mph to fps = 5280/3600 Conversion = 1.47 For 70 mph, D= 257 feet For –Factors Affecting PIEV: Age Age Fatigue Fatigue Complexity of Cues Complexity Presence of Drugs or Alcohol Presence Pedestrian Characteristics Pedestrian –Walking Speed: 4-5 feet per second –Perception and Reaction Time is 7 seconds Bicycles and Bicyclists Charact. Bicycles – AASHTO three classes. A (experienced), B, and C (Children) – Min. design speed is 20 mph – Upgrade and downgrade speeds: 831 mph – Crossing an intersection: 8 mph – Acceleration rate: 3.5 feet/ seconds square Vehicle Characteristics Vehicle –“Design Vehicles”: What? Why? How? –AASHTO Standards for: Height Height Width Width Length Length Minimum and Maximum Minimum Turning Radii Vehicle Acceleration Vehicle –Rate of Acceleration vs. Initial Speed Large passenger cars: 10 Large mph/sec Tractor-trailers: 2 mph/sec Tractor –Impact of vehicle performance on Road Design Road Traffic operations Traffic –Truck Performance on Grades Dynamic Characteristics Dynamic – Air Resistance Ra = 0.50 *(2.15*p*CD*A*U2)/g Ra = Air Resistance (lb) p = density of air CD = Drag Coefficient A = Cross Section Area (ft2) U = Speed (mph) g= Acceleration of gravity Dynamic Characteristics Cont…. Dynamic – Grade Resistance Grade Resistance = Weight * Grade – Rolling Resistance Rr = ( Crs + 2.15*Crv*U2)W Rr = Rolling Resistance in lb Crs = 0.12 for passenger cars U = Speed in mph W = gross weight in lb Dynamic Characteristics Cont…. Dynamic – Curve Resistance Rc = 0.5*(2.15*U2*W)/(gR) Rc = Curve Resistance in lb U = Speed in mph R = Curve radius in ft – Power Requirement HP = (1.47*RU)/550 Resistances Plot Resistances Passenger Car Resistances 450.0 400.0 350.0 300.0 250.0 200.0 150.0 100.0 50.0 0.0 10 20 30 40 Sp eed Air Resist ance Rolling Resist ance Curve Resist ace 50 60 70 80 Resistance Horse Power Plot Resistance Resistance/HP Curve 1400.0 1200.0 1000.0 800.0 600.0 400.0 200.0 0.0 10 20 30 40 Sp eed Total Resistance HP 50 60 70 80 Braking Distance Braking –Factors Braking System Braking Tire Condition Tire Roadway Surface Roadway Initial Speed Initial Braking Distance Equation Braking db = 2(V 2) U / 30( f + g ) • Proof = - 2(decl)(db)……….(1) F = (f)(N) = (f)(w/32.16)(cosine (f)(N) a) = (f)(w/32.16) (w)(sine a) + (w)(f) = (w)(sine (w/32.16)(decl) decl = (g+f)(32.16)……….(2) decl From (1) and (2) From 2 u 2 v db = / 2(g+f)(32.16) db = (V2 - U2)(1.47)2 / 2(g+f)(32.16) db = (V2 - U2) / 30(g+f) Vehicle traveling up-grade db = (V2 - U2) / 30(g-f) Vehicle traveling down-grade 2 (v 2) u •Horizontal Alignment V e+ f = 15 R 2 100 = (R )(D radians ) 100 = (R )( (D deg rees )(π ) 180 (100)(180) 5730 ≅ R= (D)(π ) D ) e = tan (a) = Super-elevation tan Rate e = 0.06-0.12 0.06 f = Coefficient of Side Friction = Coefficient 0.11-0.17 V= Speed in mph V= R = Minimum Curve Radius in Minimum feet •Proof V e+f = 15R 2 wv F = Nf = ( w cos a + sin a ) f gR wfv F = wf cos a + gR 2 2 2 sin a .......( 1 ) wv w sin a + F = ( ) cos a ........( 2 ) gR From (1 ) and ( 2 ) wfv wv ) cos a w sin a + wf cos a + sin a = ( gR gR fv v tan a + f + ( ) tan a = gR gR v v e + f + ( ef )( )= gR gR ef ≅ 0 V e+f = (32 .16 )( R ) 2 (1 .47 ) 2 2 2 2 2 2 2 •Horizontal Sight Distance zonta ht stance Proof S≤ L = R − Rcos(a/2) equation = R(1 − cos(a/2)) S a = 100 D SD a= equation 2 100 From equations 1 and 2 SD m = R(1 − cos( )) 200 V2 S = 1.47Vt + = SSD 30f 5730 D= R m m 1 Passing Sight Distance Passing Minimum PSD = d1 + d2 + d3 + d4 Minimum d1 = Perception-reaction time travel d2 = Passing vehicle in left lane d3 = Clearance between passing and opposing vehicle d4 = Opposing vehicle travel distance AASHTO PSD ranges 1000-2400 Feet Passing Sight Distance Passing Sight distance is determined for a single vehicle passing a single vehicle with the assumption that cover majority of situations observed in the realworld conditions. Exhibit 3-4 d1 =0278t1(v−m+at1 / 2); d2 =0278vt2; d3 =30−90m d4 =2d2 / 3 . . ; where: t1 = time of initial maneuver, s; a = average acceleration, km/h/s; v = average speed of passing vehicle, km/h; m = difference in speed between passing and passed vehicles, km/h; t2 = time passing vehicle occupies the left lane, s. ...
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