Introduction to Highway Engineering and Traffic Analysis อ. ธ รพจน ศ ร ไพโรจน. 28 August 2014

Transcription

1 Introduction to Highway Engineering and Traffic Analysis อ. ธ รพจน ศ ร ไพโรจน 28 August

2 About myself Ph.D. in Transportation Engineering from the Hong Kong Polytechnic university, Hong Kong. M.S. in Transportation Engineering from university of New South Wales, Australia. B.Eng. (2nd hon.) in Civil Engineering for Chiang Mai university. 2

3 Introduction 3

4 Definition Transportation engineering: The application of technological and scientific principles to the planning, functional design, operation and management of facilities for any mode of transportation... 4

5 Profession of transportation engineering Specialties in transportation: Planning Design Construction and maintenance Traffic Operations 5

6 Planning Select projects for design and construction. Planning involves: Forecast the impact of the project upon the system (e.g., transportation, environment) Setting up the specifications of the project Determining benefits and costs 6

7 Planning 7

8 Traditional Traffic & Transport planning process road based 8

9 Design Involves the specification of all the features of the project so that it can be built. geometric design (horizontal and vertical) pavement design determination of right of way, drainage structures, etc. 9

10 Traffic operations using the facility in the most efficient way such as: use of analytical models to determine the most efficient way to operate the facility the use of monitoring devices to determine actual conditions and level of service use of devices to implement control strategies 10

11 Traffic operations 11

12 Importance of the transportation necessary condition for economic growth, though not sufficient. interacts with land use determining location and character of cities and regions national security 12

13 Components of the transportation system Physical facilities: streets, highways, ports, railroads, etc. Fleets of vehicles: trucks, passenger cars, Vessels Operating bases and facilities: maintenance facilities, offices Organizations: railroads, airlines, shipping companies, private individuals 13

14 Transportation modes 14

15 Transportation modes A transportation mode is a specific way to travel, usually defined by either the physical system being used, by the technology used, or the organizational characteristics A transportation mode include: Road transport, Rail Transport, Water/sea Transport, Air Transport, Pipeline 15

16 Characteristics of Road Transport Physical possibility of providing a door to door facility Essential for feeder purposes for rail, water and air transports Practicable for the individual to own and drive his own personal conveyance Most suitable for short and medium distance traffic Subject to delays through traffic congestion, hence travel times may become unreliable 16

17 Characteristics of Rail Transport Sole user of the facility (i.e. the rail tracks) Complete control of all movements along the line Quite high speed and high capacity unit of carriage Provision of more elaborate passenger amenities (e.g. toilets, catering services, etc.) Suitable for medium and long distance traffic 17

18 Characteristics of Sea Transport International and long distance Mainly kept to short distance for passenger travel Very high capacity Slow but low cost for freight transport Very suitable for conveyance of lower classes of goods of a non perishable nature 18

19 Characteristics of Air Transport Very high speed. Low capacity and costly. Terminals usually are away from the centre of large town/city. Unhindered by physical barriers (e.g. mountain) experienced by other surface transport. Suitable for long distance travel. 19

20 Characteristics of Pipelines Continuous flow No packing is necessary Unaffected by road congestion, transhipment or difficult terrain Low demand for manpower Sole user of the facility, but expensive 20

21 Introduction to physical design of transportation facilities 21

22 Design of Highways Design of highways involves two objective: Minimization of costs Adequate safety levels Appropriate levels of safety is usually define as the level of safety that provides drivers with sufficient sight distance to allow them to safely stop their vehicles to avoid collisions. 22

23 Design Speed While designing highways and other transportation systems we use the concept of design speed Design speed is the speed used to establish the geometric features of the roadway or guideway (in case of trains) Design speed features: a) As high as practically possible (except for local streets) b) Should be higher than the typical operating speeds of the roadway or guideway c) Consistent with the speed users are expect from the facility 23

24 Perception and Reaction Perception: a) Process of extracting information from the surrounding environment b) Too much information can easily overload a human controller (driver, pilot, controller) c) Drivers and pilots can only perceive small amounts of bits/second of information Secondary tasks or activities are very dangerous and distracting (driving and using a cell phone) a) Value for perception time used in highway design is 2.5 s b) Accounts for the worse case scenario (a distracted driver) 24

25 Perception and Reaction Times 25

26 Design of Highways Design of highways involves two objective: Minimization of costs Adequate safety levels Appropriate levels of safety is usually define as the level of safety that provides drivers with sufficient sight distance to allow them to safely stop their vehicles to avoid collisions. 26

27 Sight Distance Considerations The ability of an operator to see ahead Critical in the design of transportation facilities For highways two types of analyses are critical: a) stopping sight distance b) passing sight distance 27

28 Stopping Sight Distance Two distance components are important to calculate Sight Stopping Distance (SSD): Reaction distance Distance traversed while the driver makes a decision to perceive, identify and react to an unexpected situation Braking distance Distance traversed in the physical activity of braking a vehicle 28

29 Stopping Sight Distance (SSD) For G=0 (no grade),v 2 =u 2 + 2as given v = 0, brake Thus, s = v 2 /(2a) Braking distance + Reaction distance where: SSD = stopping sight distance in ft (m), a = deceleration rate in ft/s 2 (m/s 2 ), V 1 = initial vehicle speed in ft/s (m/s), g = gravitational constant in ft/s 2 (m/s 2 ), t r = perception/reaction time in sec, and G = roadway grade (+ for uphill and for downhill) in percent/

30 Stopping Sight Distance With a =11.2 ft/s 2 (3.4 m/s 2 ), t r = 2.5 s, g = 9.81 (assuming G = 0) Then, stopping sight distance calculated in Table below. 30

31 Passing Sight Distance Applicable for two-lane roads and two-way highways. Major source of concern from a design viewpoint Many assumptions in the analysis (AASHTO, 2004): a) Overtaken vehicle travels at uniform speed b) Passing vehicle trails the overtaken vehicle c) Passing drive needs short period to perceive and react to passing maneuver d) When the passing vehicle returns to its travel lane there is enough clearance between this vehicle and the oncoming vehicle. 31

32 Passing sight distance Diagram 32

33 Assumptions in Passing Sight Distance Source: Table 3.1 in A Policy on Geometric Design of Highways and Streets, AASHTO 2004, pp

34 Initial maneuver distance (d 1 ) 34

35 Distance while passing vehicle occupies left lane (d 2 ) where: t 2 is the time the passing vehicle occupies the left lane, v is the average speed of passing vehicle (km/hr) 35

36 Clearance Length (d 3 ) 30 d 3 75 Note: this distance (d 3 ) has been found by empirical observations (slide page 31) to vary 30 to 75 meters. Distance traveled by opposing vehicle (d 4 ) d d 2 36

37 Passing Sight Distance (Design Values) Source: Table 3.1 in A Policy on Geometric Design of Highways and Streets, AASHTO 2004, pp