57
• 마찰력friction(f)
– F=µN
– µ=f(포장 형식, 운행 속도, 타이어 종류 및 형식, 기상 상태)
차량과 도로의 마찰력
58
• 정지 마찰계수의 이해
– 마찰 계수 실험 방법의 아이디어는?
– 마찰 계수 측정 시와 설계 시 차이는 어떻게 조 정할 것인가?
문제 제기?
59
W F
Coefficient of friction = F/W W
rubber tiredifferent
60
w f F
W F
61
Standard Test : ASTM
(American Society for Testing and Material)
friction test - water test
- non water test
water tank
v
62
미끄럼 저항 측정기(건기원)
63
마찰 계수의 변화
64
정지마찰계수 예
65
• 계산 예
– 70mph, f=0.29, 2.5sec(PIEV time) – ds=1.47*70*2.5+702/(30*0.29)
• driver,s choice of speed
– Swet<Sdry :70년대 – Swet=Sdry :now
• 즉 70년대에는 70mph의 설계속도라면 58mph를 가정 하고 이에 따른 SSD를 계산하였음 그러나 현재는 습윤상 태 든 건조상태 든 속도변화가 없음이 관찰되어 설계에 반영하였음
안전 제동 거리 연습
66
예)최소 300ft앞에서 안내판을 볼 수 있다고 가정 시 TOLL PLAZA로 들어가는 대기차량 길이가 150ft이 상이고, PIEV=2.5, f=0.35, 접근속도가 60mph일 때 안내판의 위치는?
Sol) Ds=1.4658*60*2.5+602/(30*0.35) =563.1ft
대기차량 길이가 150ft이므로 563.1+150=713.1ft가 됨 그 러나 sign판을 300ft 앞에서 볼 수 있으므로
최소한 필요한 거리는 713.1-300=413ft
안전 제동 거리 응용(Sign placement)
67
• 교통 사고 분석가는 다음의 최소 정보가 필요함
– 마찰계수 f – 충돌 속도
– 제동 거리 속도 공식
– 사고 전 차량의 운행 속도
– 문제) 충돌 속도(15mph), 포장의 미끄럼 자국 (L=100ft, f=0.35), 길어깨의 미끄럼 자국 (L=200ft, f=0.5)
안전 제동 거리 응용(Accident investigations)
68
* 해)
길어깨 진입 속도 계산
db=(V12-V22)/(30(f+g)) =(V12-152)/(30(0.5)=200 따라서 V1=56.8mph1
운행 속도의 계산
db=100=(V12-56.82)/(30*0.35)
V1=65.4mph , =>사고 원인 정보 제공
* Truck의 경우좀 더 거리가 필요하나 높은 위 치에 있으므로 O.K
안전 제동 거리 응용(Accident investigations)
69
Decision Sight Distance (DSD)
• When situation is unexpected or driver makes unusual maneuvers or under difficult to perceive situations
• Requires higher P/R time
• Depends on type of maneuver made and roadway setting (urban vs. rural)
70
Decision
(controlled stop, speed/path/route change) – DSD (Table 3-3)
Source: A Policy on Geometric Design of Highways and Streets (The Green Book).
Washingto n, DC.
American Association of State Highway and Transportat ion Officials, 2001 4th Ed.
71
DSD for A and B
72
DSD for C, D, and E
73
Passing Sight Distance (PSD) for Two-Lane Highways
1. The overtaken vehicle travels at uniform speed.
2. The passing vehicle has reduced speed and trails the overtaken vehicle as it enters a passing section.
3. When the passing section is reached, the passing driver needs a short period of time to perceive the clear passing section and to react to start his or her maneuver.
4. Passing is accomplished under what may be termed a delayed start and a hurried return in the face of opposing traffic. The passing
vehicle accelerates during the maneuver, and its average speed during the occupancy of the left lane is 15 km/h [10 mph] higher than that of the overtaken vehicle.
5. When the passing vehicle returns to its lane, there is a suitable clearance length between it and an oncoming vehicle in the other lane.
74
Passing Sight Distance (PSD) for Two-Lane Highways
d1 d2 d3 d4
75
Passing Sight Distance (PSD) for Two-Lane Highways
• d1—Distance traversed during perception and
reaction time and during the initial acceleration to the point of encroachment on the left lane.
• d2—Distance traveled while the passing vehicle occupies the left lane.
• d3—Distance between the passing vehicle at the end of its maneuver and the opposing vehicle.
• d4—Distance traversed by an opposing vehicle for two-thirds of the time the passing vehicle occupies the left lane, or 2/3 of d2 above.
76
Safe Passing Sight Distance
77
Distance d1
78
Distance d2, d3, d4
d3 = 30 m to 75 m (100 to 250 ft) d4 = 2*d2/3
79
Total Passing Sight Distance
80
Passing Sight Distance for Design of Two-Lane Highways
81
Important Sight Distances (cont.)
Intersection (turning/crossing) - see Ch 9 of GB
82
차례
Design Speed and Design Traffic Concepts CHUNG ANG UNIVERSITY - HEART LAB, KOREA Input
Design Speed and Design Traffic Concepts
83
Rural Local Roads
Source: A Policy on Geometric Design of Highways and Streets (The Green Book). Washington, DC.
American Association of State Highway and Transportation Officials, 2001 4th Ed.
Design Speed in Green Book
(suggested minimum design speed)
84
Design Speed in Green Book
(suggested minimum design speed)
Rural Collectors
Source: A Policy on Geometric Design of Highways and Streets (The Green Book). Washington, DC.
American Association of State Highway and Transportation Officials, 2001 4th Ed.
85
Traffic Typically Peaks twice per day
0 1000 2000 3000 4000 5000 6000 7000
12:30 AM 1:30 AM
2:30 AM 3:30 AM
4:30 AM 5:30 AM
6:30 AM 7:30 AM
8:30 AM 9:30 AM
10:30 AM 11:30 AM
12:30 PM 1:30 PM
2:30 PM 3:30 PM
4:30 PM 5:30 PM
6:30 PM 7:30 PM
8:30 PM 9:30 PM
10:30 PM 11:30 PM
12:30 AM
Time of Day Flow in vehicles per hour Highw ay Capacity
Highly Congested
Source: www.ecn.purdue.edu/~darcy 86
Traffic Counts Maps
87 http://www.iowadotmaps.com/msp/traffic/index.html
Traffic Counts Maps
88
차례
Design Speed and Design Traffic Concepts CHUNG ANG UNIVERSITY - HEART LAB, KOREA Input
Noise Analysis
See: http://www.nonoise.org/library/highway/probresp.htm and http://www.fhwa.dot.gov/environment/noise/index.htm
and http://www.fhwa.dot.gov/environment/audible/contents.htm
89
Common Sounds
Source Noise
Level (dB) Effect
Carrier deck jet operation, air raid siren 140 Painfully Loud
Jet takeoff at 200 feet 130
Disco, thunderclap 120 Maximum Vocal Effort
Auto Horn at 3 feet 110
Garbage Truck 100
Heavy Truck at 50 feet, city traffic 90 Very Annoying, hearing damage (8-hr) Alarm Clock at 2 feet, hair dryer 80 Annoying
Noise restaurant, freeway traffic, persons voice at 3 feet70 telephone use difficult Air conditioning unit at 20 feet 60 Intrusive
Light auto traffic at 100 feet 50 quiet Living room, bedroom, quiet office 40
Library, soft whisper at 15 feet 30 very quiet
10 Sound just audible 0 Hearing begins
90
http://www.nonoise.org/library/highway/traffic/traffic.htm 91