Highway Geometric Design PDF

Module #3: Highway Geometric Design Lesson Objectives: At the conclusion of this activity, you should be able to: 1. Define Highway Geometric Design. 2. Define Pavement Surface Characteristics. 3. Define road Unevenness. Pavement cross-section - features influence the life of...

Module #3: Highway Geometric Design Lesson Objectives: At the conclusion of this activity, you should be able to: 1. Define Highway Geometric Design. 2. Define Pavement Surface Characteristics. 3. Define road Unevenness. Pavement cross-section - features influence the life of the pavement and the riding comfort and safety of people. Of these, pavement surface characteristics affect both of these. Frictions and geometry of various cross- sectional elements are essential aspects of this regard. Also, the Unevenness and geometry of various cross-sectional features are crucial aspects to consider.  1. The friction between the wheels and the pavement surface, - This friction slows down the rotation of the wheels, ultimately bringing the vehicle to a stop. Adequate friction between the tires and the road surface is essential for effective braking. If there is insufficient friction, the tires can skid, leading to longer stopping distances and potential loss of control. Various factors that affect friction are: 1. Type of the pavement (like bituminous, concrete, gravel) 2. Condition of the pavement (dry or wet, hot or cold, etc) 3. Condition of the tire (new or old) 4. Speed and load of the vehicle. FRICTIONAL FORCE The frictional force that develops between the wheel and the pavement is the load Standard suggests the coefficient acting multiplied by the of longitudinal friction as 0.35- coefficient of friction and 0.4 depending on the speed and denoted as f. The choice of coefficient of lateral friction as the value of f is a highly 0.15. The former is helpful insight complex issue since it distance calculation and the depends on many variables. latter in horizontal curve design. 2. Smoothness/Roughness of the road surface - Pavement Smoothness (sometimes termed roughness – the opposite of smoothness) is ultimately a measure of the drivers’ comfort. It is commonly estimated using a pavement profile (a measure of minute elevation changes in the pavement surface).  UNEVENNESS - It is always desirable to have an even surface, but it is seldom possible to have one. It is possible to develop unevenness due to pavement failures even if constructed with high- quality pavers. Unevenness affects the vehicle: a. operating cost, b. speed, c. riding comfort, d. safety, e. fuel consumption, and f. wear and tear of tires. UNEVENNESS INDEX Unevenness index measures unevenness, the cumulative standard of vertical undulations of the pavement surface recorded per unit horizontal length of the road. An unevenness index value less than 1500 mm per km is considered good. A value less than 2500 mm per km is satisfactory up to a speed of 100 km/h, and values greater than 3200 mm/km is considered uncomfortable even for 55 km/h.  3. The light reflection characteristics of the top of pavement surface - Reflection occurs when light traveling through one material bounces off a different material. The reflected light continues to travel in a straight line, but in a different direction. The light reflection characteristics of the top of pavement surface  LIGHT REFLECTION White roads have good visibility at night but caused glare during day time. On the contrary, Black roads have no glare during the day but have poor visibility at night. Concrete roads have better visibility and less glare. The road surface must be visible at night, and light reflection is the factor that answers it. LIGHT REFLECTION ROAD STUDS OR CAT’S EYES 1. Reflective road studs 2. Solar - Powered road studs 3. LED road studs  4. Drainage to water. - Surface drainage is concerned with removing all water that is present on the pavement surface, shoulder surface or any other surface from which it may flow onto the pavement. If not systematically removed, this water can accumulate underneath and weaken the pavement structure.  Module #4: Camber and Width of Carriageway Lesson Objectives: At the conclusion of this activity, you should be able to: 1. Define camber. 2. Define Width of carriageway.  CAMBER - Surface drainage is concerned with removing all water that is present on the pavement surface, shoulder surface or any other surface from which it may flow onto the pavement. If not systematically removed, this water can accumulate underneath and weaken the pavement structure.  OBJECTIVES OF PROVIDING CAMBER: - Surface protection especially for gravel and bituminous roads. - Sub-grade protection by proper drainage quick drying of pavement which in turn increases safety.Too steep slope is undesirable for it will erode the surface.  MEASUREMENTS OF CAMBER: - Camber is measured in 1 in n or n% (Example 1 in 50 or 2%) and the value depends on the type of pavement surface. The standard values suggested for various categories of pavement are given in Table. Surface Type Heavy Rain Light Rain Concrete / 2% 1.7% Bituminous Gravel 3% 2.5% Earthen 4% 3.0% TYPES OF CAMBER: 1. PARABOLIC OR BARREL CAMBER - This type of camber consists of a continuous curve. The curve is either parabolic or elliptical. This type of camber is mainly used for those roads where fast moving vehicles pass frequently. TYPES OF CAMBER: 2. STRAIGHT OR SLOPED CAMBER - This type of camber is made by meeting two straight surfaces in the crown. Crown is the central point in the surface of the road. The shape of the edges make difficulties for the traffic. That is why it is not used frequently. TYPES OF CAMBER: 3. COMPOSITE/COMBINATION CAMBER - It is a combination of sloped/straight and parabolic camber  CARRIAGEWAY - The actual part of the road where vehicles travel, typically referring to the paved section.  CARRIAGEWAY 1. Traffic Lane Width: - A traffic lane must accommodate the width of a vehicle plus a clearance on either side to improve safety and operating speed. - The maximum permissible width of a vehicle is 2.44 m, and the desirable side clearance for a single-lane road is 0.68 m.  CARRIAGEWAY 2. Single-Lane Road: - To provide enough room for the vehicle and side clearances, the minimum lane width for a single-lane road is 3.75 m. 3. Two-Lane Road: - For two-lane roads, the side clearance required is about 0.53 m on each side (1.06 m in total). - This results in a minimum width of 3.5 m per lane, making the total carriageway width for a two-lane road 7.0 m. PHILIPPINE CARRIAGEWAY SYSTEM PHILIPPINE CARRIAGEWAY SYSTEM CAMBER IN PHILIPPINE CARRIAGEWAY SYSTEM