Highway Engineering Module #7-9 PDF

CIE 122: HIGHWAY AND RAILROAD ENGINEERING Engr. John Paul R. Tumangan  Module #7: Sight Distance Lesson Objectives: After this activity, you should be able to: 1. Define the meaning of Sight distance. 2. Identify type of Sight distance. Sight Distance - Sight distance is the length of r...

CIE 122: HIGHWAY AND RAILROAD ENGINEERING Engr. John Paul R. Tumangan  Module #7: Sight Distance Lesson Objectives: After this activity, you should be able to: 1. Define the meaning of Sight distance. 2. Identify type of Sight distance. Sight Distance - Sight distance is the length of roadway visible to a driver. - Stopping sight distance (SSD) is the minimum sight distance available on a highway at any spot having sufficient length to enable the driver to stop a vehicle traveling at design speed, safely without collision with any other obstruction. Sight Distance Overview - AASHTO (2011) - Stopping Sight Distance (SSD) Sight Distance Overview - The safe and efficient operation of vehicles on the road depends very much on the visibility of the road ahead of the driver. Thus the geometric design of the road should be done such that any obstruction on the road length could be visible to the driver from some distance ahead. This distance is said to be the sight distance. - Sight distance available from a point is the actual distance along the road surface, over which a driver from a specified height above the carriage way has visibility of stationary or moving objects. Types of Sight Distance Three sight distance situations are considered for design: 1. Stopping sight distance (SSD) or the absolute minimum sight distance. 2. Intermediate sight distance (ISD) is defined as twice SSD 3. Overtaking sight distance (OSD) for safe overtaking operation SIGHT DISTANCES - Intermediate sight distance (ISD) provides an additional margin of safety for road sections where overtaking is not allowed or feasible, ensuring the vehicles have adequate visibility to stop or slow down. - Overtaking sight distance (OSD) is the minimum distance required for a vehicle to safely overtake another vehicle on a two way road without causing danger to an oncoming traffic or the overtaken vehicle. Safe sight distance to enter into an intersection. The most important consideration in all these is that at all times the driver traveling at the design speed of the highway must have sufficient carriageway distance within his line of vision to allow him to stop his vehicle before colliding with a slowly moving or stationary object appearing suddenly in his own traffic lane. The computation of sight distance depends on: Reaction time of a driver is the time taken from the instant the object is visible to the driver to the instant when the brakes are applied. In practice, all these times are usually combined into a total perception reaction time suitable for design purposes as well as for easy measurement. Many of the studies show that drivers require about 1.5 to 2 secs under normal conditions. However, taking into consideration the variability of driver characteristics, a higher value is normally used in design. For example, standard suggests a reaction time of 2.5 secs. Stopping Sight Distance where, V - design speed (km/h) T - reaction perception time (2.5s) A - deceleration rate (3.4 m/s^2) Intermediate Sight Distance ISD = 2 * SSD Overtaking Sight Distance Overtaking Sight Distance Overtaking Sight Distance where, Vb - speed of overtaking vehicle (km/h) tb - time to initiate overtaking (usually 2-3 seconds) f - coefficient of longitudinal friction Vo - speed of opposing vehicle (km/h) to - time to opposing vehicle to cover its part of overtaking zone Sample Problem: Stopping Sight Distance Intermediate Sight Distance ISD = 2 * SSD Overtaking Sight Distance Overtaking Sight Distance Module #8: Traffic Signs Lesson Objectives: After this activity, you should be able to: 1.. Define Traffic signs. 2. Identify type of road user communicating tools. Traffic Signs - Traffic signs or road signs are signs erected at the side of or above roads to give instructions or provide information to road users. Traffic Signs Overview - Traffic signs describe a range of sign that are used to indicate or enforce traffic laws, regulations or requirements which apply either at all times or at specified times or places upon a street or highway, the disregard of which may constitute a violation, or signs in general that regulate public behavior in places open to the public. - Traffic signs in the Philippines are standardized in the Road Signs and Pavement Markings Manual, published by the Department of Public Works and Highways. Traffic Signs Overview - Traffic control device is the medium used for communicating between traffic engineer and road users. Unlike other modes of transportation, there is no control on the drivers using the road. Here traffic control devices come to the help of the traffic engineer. - The major types of traffic control devices used are - traffic signs, road markings, traffic signals and parking control. - Different types of traffic signs are regulatory signs, warning signs and informatory signs. Requirements of traffic control devices 1. The control device should fulfill a need: Each device must have a specific purpose for the safe and efficient operation of traffic flow. 2. It should command attention from the road users: This affects the design of signs. For commanding attention, proper visibility should be there. Also, the sign should be distinctive and clear. The sign should be placed in such a way that the driver requires no extra effort to see the sign. Requirements of traffic control devices 3. It should convey a clear, simple meaning: Clarity and simplicity of message is essential for the driver to properly understand the meaning in short time. The use of color, shape and legend as codes becomes important in this regard. The legend should be kept short and simple so that even a less educated driver could understand the message in less time. 4. Road users must respect the signs: Respect is commanded only when the drivers are conditioned to expect that all devices carry meaningful and important messages. Over use, misuse and confusing messages of devices tends the drivers to ignore them. Requirements of traffic control devices 5. The control device should provide adequate time for proper response from the road users: This is again related to the design aspect of traffic control devices. The sign boards should be placed at a distance such that the driver could see it and gets sufficient time to respond to the situation. For example, the STOP sign which is always placed at the stop line of the intersection should be visible for at least one safe stopping sight distance away from the stop line. COMMUNICATION TOOLS A number of mechanisms are used by the traffic engineer to communicate with the road user. These mechanisms recognize certain human limitations, particularly eyesight. Messages are conveyed through the following elements. 1. Shape 2. Color 3. Legend 4. Pattern 1. SHAPE It is the second element discerned by the driver next to the color of the device. The categories of shapes normally used are circular, triangular, rectangular, and diamond shape. Two exceptional shapes used in traffic signs are octagonal shape for STOP sign and use of inverted triangle for GIVE WAY (YIELD) sign. CIRCLES (gives order) TRIANGLES (warns) RECTANGLES (informs) 2. COLOR It is the first and most easily noticed characteristics of a device. Usage of different colors for different signs is important. The most commonly used colors are red, green, yellow, black, blue, and brown. Consistent use of colors helps the drivers to identify the presence of sign board ahead. Blue circles generally give a mandatory instruction, such as ‘turn left’, or indicate a route available only to particular classes of traffic, e.g. buses and cycles only Red rings or circles tell you what you must not do, e.g. you must not exceed 30 mph, no vehicles over the height shown may proceed. Blue rectangles are used for information signs except on motorways, where blue is used for direction signs. Green rectangles are used for direction signs on primary routes. White rectangles are used for direction signs on non-primary routes, or for plates used in combination with warning and regulatory signs. 3. LEGEND This is the last element of a device that the driver comprehends. This is an important aspect in the case of traffic signs. For the easy understanding by the driver, the legend should be short, simple and specific so that it does not divert the attention of the driver. Symbols are normally used as legends so that even a person unable to read the language will be able to understand that. There is no need of it in the case of traffic signals and road markings. 3. LEGEND 4. PATTERN It is normally used in the application of road markings, complementing traffic signs. Generally solid, double solid and dotted lines are used. The frequent and consistent use of pattern to convey information is recommended so that the drivers get accustomed to the different types of markings and can instantly recognize them.  Module #9: Types of Traffic Signs Lesson Objectives: After this activity, you should be able to: 1. Define the meaning of regulatory sign. 2. Identify type of traffic signs. Types of Traffic Signs - There are several hundreds of traffic signs available covering wide variety of traffic situations. They can be classified into three main categories. 1. Regulatory Signs - These signs require the driver to obey the signs for the safety of other road users. 2. Warning Signs - These signs are for the safety of oneself who is driving and advice the drivers to obey these signs. 1. REGULATORY SIGNS Also called mandatory signs because the drivers must obey these signs for the safety of other road users. If the driver fails to follow them, the control agency has the right to take legal action against the driver. These signs generally have a black legend on a white background. They are circular with red borders. The regulatory signs can classify into: a. Right of Way Series b. Speed Series c. Movement Series d. Parking Series e. Pedestrian Series f. Miscellaneous RIGHT OF WAY SERIES These include two unique signs that assign the right of way to the selected approaches of an intersection. They are the STOP sign and GIVE WAY sign for example, when one minor road and major road meets at an intersection, preference should be given to the vehicles passing through the major road. Hence the give way sign board will be placed on the minor road to inform the driver on the minor road that he should give way for the vehicles on the major road. Stop sign is an example of regulatory signs that comes in right of way series which requires the driver to stop the vehicle at the stop line. RIGHT OF WAY SERIES SPEED SERIES Number of speed signs may be used to limit the speed of the vehicle on the road. They include typical speed limit signs, truck speed, minimum speed signs etc. Speed limit signs are placed to limit the speed of the vehicle to a particular speed for many reasons. Separate truck speed limits are applied on high-speed roadways where heavy commercial vehicles must be limited to slower speeds than passenger cars for safety reasons. Minimum speed limits are applied on high-speed roads like expressways, freeways etc. where safety is again a predominant reason. SPEED SERIES MOVEMENT SERIES They contain a number of signs that aspect specific vehicle maneuvers. These include turn signs, alignment signs, exclusion signs, one-way signs etc. Turn signs include turn prohibitions and lane use control signs. Lane use signs make use of arrows to specify the movements which all vehicles in the lane must take. Turn signs are used to safely accommodate turns in unsignalized intersections. MOVEMENT SERIES PARKING SERIES They include parking signs which indicate not only parking prohibitions or restrictions, but also indicate places where parking is permitted, the type of vehicle to be parked, duration for parking etc. PARKING SERIES PEDESTRIAN SERIES They include both legend and symbol signs. These signs are meant for the safety of pedestrians and include signs indicating pedestrian only roads, pedestrian crossing sites etc. PEDESTRIAN SERIES MISCELLANEOUS Wide variety of signs that are included in this category are: a "KEEP OF MEDIAN" sign, signs indicating road closures, signs restricting vehicles carrying hazardous cargo or substances, signs indicating vehicle weight limitations etc. MISCELLANEOUS PROHIBITION  Module #10: Warning and Informative Signs Lesson Objectives: After this activity, you should be able to: 1. Define the meaning of warning & informative signs. 2. How important are these signs in the roadway. Warning Signs A warning sign is a type of sign which indicates a potential hazard, obstacle or condition requiring special attention. Some are traffic signs that indicate hazards on roads that may not be readily apparent to driver. It advice the driver to obey the rules. Most of the shape used is upward triangular or diamond shape. Warning Signs Various situations where warning signs might be used. Warning signs might be used to indicate any number of hazards. a) no passing zones b) railroad crossings c) school zones d) sharp curves, e) intersections ahead, or animal crossings. Warning Signs Warning Signs Warning Signs Warning Signs Warning signs are meant for the own safety of drivers. They call for extra vigilance from the part of drivers while information signs being an assist signs have been growing in visibility due to the explosion of sign technologies and they do affect the geometric of the roadway. Informative or Guide Signs Informative signs also called guide signs are provided to assist the drivers to reach their desired destinations. These are predominantly meant for the drivers who are unfamiliar to the place. Informative or Guide Signs Informative or Guide Signs Type of signs are: a) route markers b) destination signs c) mile posts, service Route Markers Route markers are used to identify numbered highways. They have designs that are distinctive and unique. They are written black letters on yellow background. Route Markers Destination Signs Destination signs are used to indicate the direction to the critical destination points, and to mark important intersections. Distance in kilometre (km) is sometimes marked to the right side of the destination. They are, in general, rectangular with the long dimension in the horizontal direction. Mileposts are provided to inform the driver about the progress along a route to reach his destination Destination Signs Mile posts / service  Module #11: Road Markings Lesson Objectives: After this activity, you should be able to: 1. Define the meaning of Road Marking. 2. Identify type and use of road markings. Road Markings The road markings are defined as lines, patterns, words or other devices, except signs, set into applied or attached to the carriageway or kerbs or to objects within or adjacent to the carriageway, for controlling, warning, guiding and informing the users. Road Markings Overview Road markings the essential purpose of road markings is to guide and control traffic on a highway. They supplement the function of traffic signs. The markings serve as a psychological barrier and signify the delineation of traffic path and its lateral clearance from traffic hazards for the safe movement of traffic. Road Markings Classifications: 1. Longitudinal Road Markings 2. Transverse Road Markings Longitudinal Road Markings Longitudinal markings are placed along the direction of traffic on the roadway surface, for the purpose of indicating to the driver, his proper position on the roadway. Longitudinal markings are provided for separating traffic flow in the same direction and the predominant color used is white. Yellow color is used to separate the traffic flow in opposite direction and also to separate the pavement edges. Longitudinal Road Markings The lines can be either broken, solid or double solid. Broken lines are permissive in character and allow crossing with discretion, if track situation permits. Solid lines are restrictive in character and does not allow crossing except for entry or exit from a side road or premises or to avoid a stationary obstruction. Double solid lines indicate severity in restrictions and should not be crossed except in case of emergency. Transverse Road Markings Transverse markings are marked across the direction of traffic. They are marked at intersections. The site conditions play a very important role. The type of road marking for a particular intersection depends on several variables such as speed characteristics of traffic, availability of space. Stop line markings, markings for pedestrian crossing, direction arrows are some of the markings on approaches to intersections. Examples of Road Markings Examples of Road Markings Examples of Road Markings Examples of Road Markings Examples of Road Markings Examples of Road Markings Examples of Road Markings Examples of Road Markings Examples of Road Markings Examples of Road Markings Examples of Road Markings Other Examples of Road Markings Other Examples of Road Markings Other Examples of Road Markings Other Examples of Road Markings Other Examples of Road Markings Other Examples of Road Markings Other Examples of Road Markings Other Examples of Road Markings Other Examples of Road Markings Other Examples of Road Markings Other Examples of Road Markings Other Examples of Road Markings Other Examples of Road Markings Other Examples of Road Markings Other Examples of Road Markings Other Examples of Road Markings Other Examples of Road Markings Other Examples of Road Markings  Module #12: Road Pavements Lesson Objectives: After this activity, you should be able to: 1. Define the meaning of Road Pavement. 2. Identify type and requirements of road pavements. Road Surface or Pavement A road surface or pavement is the durable surface material laid down on an area intended to sustain vehicular or foot traffic, such as a road or walkway. Road Surface or Pavement Overview A highway pavement is a structure consisting of superimposed layers of processed materials above the natural soil subgrade, whose primary function is to distribute the applied vehicle loads to the sub-grade. The pavement structure should be able to provide a surface of acceptable riding quality, adequate skid resistance, favorable light reflecting characteristics, and low noise pollution. Types of Road Surface or Pavement 1. Flexible Pavement 2. Rigid Pavement Flexible Pavement will transmit wheel load stresses to the lower layers by grain-to-grain transfer through the points of contact in the granular structure. The wheel load acting on the pavement will be distributed to a wider area, and the stress decreases with the depth. Taking advantage of these stress distribution characteristic, flexible pavements normally have many layers. Hence, the design of flexible pavement uses the concept of layered system. Flexible Pavement Based on this, flexible pavement may be constructed in a number of layers and the top layer has to be of best quality to sustain maximum compressive stress, in addition to wear and tear. The lower layers will experience lesser magnitude of stress and low-quality material can be used. Flexible Pavement Flexible pavements are constructed using bituminous materials. These can be either in the form of surface treatments asphalt concrete surface courses. Flexible pavement layers react the deformation of the lower layers on to the surface layer. In the case of flexible pavement, the design is based on overall performance of flexible pavement, and the stresses produced should be kept well below the allowable stresses of each pavement layer. Flexible Pavement Rigid Pavement have sufficient flexural strength to transmit the wheel load stresses to a wider area below. Compared to flexible pavement, rigid pavements are placed either directly on the prepared subgrade or on a single layer of granular or stabilized material. Since there is only one layer of material between the concrete and the subgrade, this layer can be called as base or sub-base course. Rigid Pavement In rigid pavement, load is distributed by the slab action, and the pavement behaves like an elastic plate resting on a viscous medium. Rigid pavements are constructed by Portland cement concrete (PCC) and should be analyse by plate theory instead of layer theory, assuming an elastic plate resting on viscous foundation. Bending of the slab due to wheel load and temperature variation and the resulting tensile and flexural stress. Rigid Pavement Rigid Pavement Classification Rigid pavements can be classified into four types: 1. Jointed plain concrete pavement (JPCP) 2. Jointed reinforced concrete pavement (JRCP) 3. Continuous reinforced concrete pavement (CRCP) 4. Prestressed concrete pavement (PSCP) Jointed plain concrete pavement (JPCP) Jointed reinforced concrete pavement (JRCP) Continuous reinforced concrete pavement (CRCP) Prestressed concrete pavement (PSCP) An ideal pavement should meet the following requirements: Sufficient thickness to distribute the wheel load stresses to a safe value on the sub-grade soil Structurally strong to withstand all types of stresses imposed upon it Adequate coefficient of friction to prevent skidding of vehicles Smooth surface to provide comfort to road users even at high speed An ideal pavement should meet the following requirements: Produce least noise from moving vehicles Dust proof surface so that traffic safety is not impaired by reducing visibility Impervious surface, so that sub-grade soil is well protected, and Additional Topic: Designing of Pavement Design of Road Pavement A road surface or pavement is the durable surface material laid down on an area intended to sustain vehicular or foot traffic, such as a road or walkway.