Geometric Design of Highways PDF

GEOMETRIC DESIGN OF HIGHWAYS Presenters: Cagang, Ranul Marino Hernandez, Dhonna Marie Lituanas, Lysander John Mendanio, Jannah Maye Recto, Rozilli Zoe GEOMETRIC DESIGN Highway geometric design deals with dimensions and layout of visible features like horizontal and vertica...

GEOMETRIC DESIGN OF HIGHWAYS Presenters: Cagang, Ranul Marino Hernandez, Dhonna Marie Lituanas, Lysander John Mendanio, Jannah Maye Recto, Rozilli Zoe GEOMETRIC DESIGN Highway geometric design deals with dimensions and layout of visible features like horizontal and vertical alignments, sight distances, and intersections.  INTERSECTION & INTERCHANGES SUPERELEVATION WIDENING CROSS HORIZONTAL SECTION CURVES  GENERAL PRINCIPLES FOR GEOMETRIC DESIGN Must be suitable for the traffic volume Must be consistent Must be pleasing Must be complete Shall be as simple as possible from the standpoint of the builder. Should be such that the finished road can be maintained at the least cost. Must be safe for driving and should ensure confidence for motorists.  INTERSECTION & INTERCHANGES SUPERELEVATION WIDENING CROSS HORIZONTAL SECTION CURVES CROSS SECTION refers to the design and layout of the various elements that make up the roadway.  TYPICAL HIGHWAY The cross section of a typical highway has latitude of variables to consider such as: The volume of traffic Character of the traffic Speed of the traffic Characteristics of motor vehicles and of the driver  DESIGNING HIGHWAY Originally, the total surface width of the roadway was only 4.50 meters, but due to the increased number of vehicles using the roadway, the width was adjusted to 4.80 to 5.40 meters. Lately, the width of the road was standardized to 3.00 m for first class paved one lane highway, and now 3.60 meters wide surface was adopted as standard for freeways and other major traffic roadways, although there is strong demand to increase it further from 3.60 to 4.20 meters.  DESIGNING HIGHWAY For Two Lane Rural Highways, a 7.20 meters wide surface is required for safe clearance between commercial vehicles and is recommended for main highways. For Collector Roadway, 6.00 meters wide surface is acceptable only for low volume traffic including few trucks traveling there. For Local Rural Roadway, the minimum surface width is 4.80 meters for a 30 km / hr design speed.  DESIGNING HIGHWAY For Urbair Roadway, the minimum design width is 3.60 meters although 3.00 meters is allowed where space is limited. Where there are heavy meetings or overtaking between cars and trucks, air disturbances sometimes cause side collisions between passing vehicles when sweryed within or out of their lanes. Motorists are requesting wider lanes  CROSS SECTION ELEMENTS Pavement Traffic Barriers Lane Widths Medians Shoulders Tunnels Horizontal Clearance to Pedestrian Crossings Obstruction Curb-Cut Ramps Curbs Bicycle Facilities Sidewalks Bus Turnouts Drainage Channels and Side Slopes  PAVEMENT The pavement is regarded as the running surface, excluding shoulders, regardless of the width of the pavement courses which support the running surface.  LANE WIDTHS The width of pavement is determined by the lane width, which depends on the width and size of vehicles, speed of travel, the annual average daily traffic and the width of shoulders.  SHOULDERS Road shoulder or verge is defined as that portion of the roadway between the edge of the traffic lane and the edge of the ditch, gutter, curb or side slope.  IMPORTANCE 1. Road shoulder serves as a place for vehicles to stop when disabled or for some other purposes. Road shoulders considerably reduce road accidents. 2. The road capacity is decreased and accident opportunity increases if the shoulder is too narrow or omitted in the design. 3. Shoulders should be continuous along the full length of the roadway. It also adds structural strength to the road pavement. 4. Shoulder increases the horizontal sight distance on curves. It reduces accident potential when vehicles stop during emergencies. HORIZONTAL CLEARANCE TO OBSTRUCTION Right-of-way should be of sufficient width to include all the cross section elements with good balance throughout. This is particularly pertinent at intersections with other highways and in areas where roadsides are apt to become developed.  CURBS A curb, by definition, incorporates some raised or vertical element. Configurations include both vertical and sloping curbs, designed as a separate unit or integral with the pavement.  SIDEWALKS Wherever roadside and land development conditions affect regular pedestrian movement along a highway, a sidewalk or path suitable to the conditions should be provided. DRAINAGE CHANNELS AND SIDE SLOPES On expressways and other arterials with relatively wide roadsides, drainage channels and side slopes should be designed to provide a reasonable opportunity for a driver to recover control of an errant vehicle.  TRAFFIC BARRIERS Traffic barriers are used to prevent vehicles that leave the traveled way from colliding with objects that have greater crash severity potential and the barrier itself.  MEDIANS A median is the portion of a highway separating opposing directions of the traveled way, and are highly desirable on arterials carrying four or more lanes. TUNNELS Tunnels may be constructed to carry highways under or through natural obstacles or to minimize the impact of a highway on the community.  PEDESTRIAN CROSSINGS Marked pedestrian crosswalk is one approach to get pedestrians safely across the street, though they are often best used in combination with other treatments. Crossings may be at an intersection or midblock, and both cases should be considered in assessing the frequency of crossing opportunities. CURB-CUT RAMPS When designing a project that includes curbs and adjacent sidewalks proper attention should be given to the needs of persons with disabilities, such as those with mobility issues or visual impairment. Curb ramps are necessary to provide access between the sidewalk and the street at pedestrian crossings.  BICYCLE FACILITIES Cycle facilities are designated spaces within the street that are specifically designed for the movement of cyclists. BUS TURNOUTS Bus turnouts serve to remove the bus from the traveled way. The location and design of turnouts should provide ready access in the safest and most efficient manner.  HORIZONTAL (CIRCULAR)CURVES ROAD ALIGNMENT - refers to the horizontal and vertical layout of a roadway, including its path, curves, tangents, and changes in elevation. -It dictates the route a road follows, influencing how vehicles travel along it.  DEFINITION The position or the layout of the highway on the ground which includes straight and curved paths. provide safe & continuous operation at a uniform design speed for substantial lengths of highways ELEMENTS OF HORIZONTAL CURVE 1. Tangent (Straight Sections) 2. Curves  MAJOR DESIGN CONSIDERATIONS: safety grade profile construction cost type of facility aesthetics design speed topography  GRADE PROFILE & ALIGNMENT multilane highways may be of a two-lane roads in higher order lower order. due to following the terrain Right-of-way at interchange sites largely impacts expressway alignment in cities.  TOPOGRAPHY Topography- contorls curve radius. Design speed & sight distance into a large extent.  DESIGN GUIDELINES FOR HORIZONTAL ALIGNMENT IN HIGHWAYS: Radius of Curve Length of Curve Superelevation Highway Median Stopping & Passing Distance  RADIUS CURVE design speed & maximum superelevation controls the maximum degree of curvature. The road should follow the terrain and achieve alignment with reasonable cost. According to DPWH, Department Order No. 11 series of 2014, Tourisms Roads should have Radius of Horizontal Curve Minimum of 50 m  CURVE RADIUS DESIGN: 1. Keep curves flat- for safe passing sight distance based on design speed. 2. Use simple curves- such as whole degrees or multiples of 10 minutes for easier layout. 3. Adjust superelevation- For steep grades (over 5%), adjust superelevation for uphill/downhill speed differences. 4. Marginal passing sight distance for curve radii. 5. Minimum stopping distance for design speed at all points. TABLE 2-9: DEGREE OF CURVES TABLE 3-12: MINIMUM DESIGN RADIUS USING LIMITING VALUES OF E &F  LENGTH OF CURVE Recommended Length, ideally, the straight part (tangent) between these curves should be atleast 50m long. Minimum Length if space is really tight, the shortest acceptable tangent length is 30m.  SUPERELEVATION helps manage the centrifugal force that pushes a vehicle outward while navigating a curve. provides balance by tilting the road surface so that the outer edge is higher than the inner edge, preventing skidding and improving ride comfort.  SUPERELEVATION DESIGN IMPLEMENTATION Gradual Transition- Wider Roads: For multi-lane Superelevation should start roads: on the tangent before the Four-lane roads: curve and reach full value Increase runoff length beyond the curve’s start. by 50%. Superelevation runoff length Six-lane roads: should be 60% to 80% of the Increase runoff length total length of superelevation by 100%. to ensure smooth transitions.  HIGHWAY MEDIAN Purpose and Advantages of Medians: 1. Safety and Conflict Reduction: Headlight Glare Reduction Accident Prevention 2. Space Utilization: Left Turn Lanes Turning Space  STOPPING DISTANCE minimum distance required for a vehicle, travelling at the design speed, to stop before reaching an object in its path. Vf= velocity in m/s t= perception-reaction time f= coefficient of friction between tires & pavement G= average grade of roadway  STOPPING DISTANCE SAMPLE PROBLEM Determine the minimum sight distance on a -3.5% grade fir a design speed of 110 kph. Coefficient of friction between tires & pavement is 0.28. Driver’s reaction time including perception time is 2.5 sec.  STOPPING DISTANCE Solution source: https://www.youtube.com/watch?v=lzrL8CCjnbs&list=PLnSQKeGTilrEZCEXIS5lRAy_RNVBi_l-g&index=5  PASSING DISTANCE the minimum distance required to safely make a normal passing maneuver on 2-lane highways a passing speeds common to nearly all drivers, commensurate with design speed.  PASSING DISTANCE SAMPLE PROBLEM: Compute the passing sight distance that vehicle A could move while overtaking the slow moving vehicle B before meeting the on-coming vehicle C. Speed of car A= 96 kph Speed of car B= 88kph Perception-reaction time= 2.5 sec. Average acceleration= 2.4 m/sec^2 Time the passing vehicle occupies the left lane = 10. 4 s Distance between the passing vehicle at the end of its manuever & the opposing vehicle = 84 m  PASSING DISTANCE Solution: source: https://www.youtube.com/watch?v=lzrL8CCjnbs&list=PLnSQKeGTilrEZCEXIS5lRAy_RNVBi_l-g&index=5  TYPES OF HORIZONTAL ALIGNMENT SPIRAL COMPOUND CURVE (TRANSITION) CURVE 2 4 1 3 SIMPLE REVERESE CURVE CURVE SIMPLE CURVE Normal horizontal curve which connects two straight lines with constant radius. PURPOSES: Use simple curves for low-traffic roads. Position bridges entirely on a simple curve.  CALCULATING SIMPLE CURVE Terminologies in Simple Curve PC = Point of curvature. PT = Point of tangency. PI = Point of intersection of the tangents. T = Length of tangent from PC to PI and from PI to PT. R = Radius of simple curve, or simply radius. 02 - WEBSITE L = Length of chord from PC to PT. Lc = Length of curve from PC to PT. E = External distance, the nearest distance from PI to the curve. m = Middle ordinate, the distance from midpoint of curve to midpoint of chord. I = Deflection angle (also called angle of intersection and central angle). x = offset distance from tangent to the curve. θ = offset angle subtended at PC between PI and any point in the curve D = Degree of curve. Sub chord = chord distance between two adjacent full stations.  LENGTH OF LONG CHORD FORMULAS LENGTH OF TANGENT LENGTH OF CURVE EXTERNAL DISTANCE ARC BASIS MIDDLE ORDINATE CHORD BASIS COMPOUND CURVE -compound curve is a combination of two or more simple curves w/ different radi. -both or all the curves lies on the same common tangent. PURPOSES: Use compound curves for smooth transitions. Fit curves to the terrain and control speeds.  COMPOUND CURVE DESIGN when the design speed of a torning roadway is 70 kph or less, compound curvature should be used to enhance: minimize right-of-way driver comfort & safety However, it is important to ensure that: compound curve length should not be too short. short curve fails to properly reduce speed between the tangent & the sharp curve. 3-17 MIMIMUM LENGTHS OF CIRCULAR ARCS OF DIFFERENT COMPOUND CURVE RADII  ISSUES W/ COMPOUND CURVE OF DIFFERENT RADII: abrupt sharpness changes- compound curves that change abruptly in sharpness can be confusing for drivers. differences in radii - it may cause drivers to shift positions w/in their lane or veer out of it. design quality- such sudden changes are considered poor design as they negatively impact driver safety & vehicle control.  REVERSE CURVE consists of two consecutive curves turning in opposite directions, connected by a common tangent. typically used when the road alignment needs to change direction quickly due to geographical constraints or design considerations.  REVERSE CURVE ON MODERN HIGHWAYS Usage: Rarely used on modern highways. Acceptable Practice: With Easements: Reverse curves are acceptable if there are proper easements (gradual transitions) between them. Without Easements: Curves in opposite directions should be separated by a tangent section of several meters.  SPIRAL (TRANSITION) CURVE A spiral curve in highway design is a transition curve used to connect a straight section of road (tangent) with a circular curve (or between two curves with different radii).  When vehicle travels at high-speed along a path of tangents connected by sharp curves, it can lead to discomfort for passengers. As the vehicle approaches a curve, superelevation tilts the car inward, but passengers remain upright since there’s no centrifugal force acting on them. Upon entering the curve, full centrifugal force suddenly pulls them outward, creating discomfort. This cycle repeats as the vehicle exits the curve. To improve comfort, spiral curves (also known as Euler spirals or Clothoids) are introduced. These curves gradually transition from a straight tangent to a circular arc, allowing centrifugal force to develop smoothly. The Clothoid curve features a radius that varies from infinity at the tangent end to the radius of the circular arc at the other end.  DESIGN CONSIDERATIONS: For Highways: For highways with high traffic volumes, the geometric design should include spiral curves to enhance comfort and safety For Low Traffic Roads: Roads with low traffic volumes are often designed with simple curves. However, for better performance and comfort on higher traffic roads, transition curves are recommended.  PRINCIPAL ADVANTAGES OF TRANSITION CURVES IN HORIZONTAL ALIGNMENT: 1. Gradual Change in Steering and Centrifugal Force: Steering Adjustment: When a vehicle transitions from a straight path to a curved path, the steering angle needs to change to match the curve’s degree and the vehicle’s speed. This adjustment takes time due to the driver's reaction time. Centrifugal Force: A sudden application of centrifugal force can occur, especially with high speeds and sharp curves, creating discomfort and potential hazards. Transition Curve Benefits: A transition curve (spiral curve) provides a gradual change from a straight path to a curved path, allowing for smoother adjustment of steering and reducing the sudden impact of centrifugal force. 2. Superelevation Run-Off: Gradual Superelevation: Transition curves allow for a gradual increase in superelevation, balancing the curvature radius and the superelevation amount. This helps in achieving proper equilibrium. Distribution Issue: Common practice distributes superelevation run-off with 1/3 on the curve and 2/3 on the tangent, which does not fully satisfy physical laws as it does not completely counteract the forces throughout the entire length of the curve. 3. A spiral transition curve also facilitate the transition in width where the travelled way is widened on a circular curve use of spiral transitions provides flexibility in accomplishing the widening of sharp curves.  GENERAL CONTROLS 1. DIRECTION CONSISTENCY Conform to Topography: Alignments should follow natural contours to minimize disruption and maintain a flowing line. Avoid sharp tangents that cut through the terrain. 2. Curve Design Flat Curves Preferred: Use flat curves and avoid maximum-degree curves except under critical conditions. Consistent Alignment: Avoid sharp curves at the ends of long tangents. Prevent sudden changes from easy to sharply curving alignment. 3. Curve Length and Tangents Sufficient Length for Small Deflection Angles: Ensure curves are long enough to avoid a “kink” appearance. High Fills: Use tangents or flat curvature on long high fills.  GENERAL CONTROLS 4. Curve Compounding Caution in Compound Curves: The radius of the flatter curve should not exceed 50% of the sharper curve’s radius. Use intermediate curves or spirals for smoother transitions if compounding is necessary. Avoid Abrupt Reversal: Use sufficient tangent or spiral length between two curves. 5. Avoid Broken Back Curvature: Instead of two close curves, use spirals or longer curves. 6. Coordinate Alignments: Align horizontal and vertical profiles. 7. Bridges and Curves: Avoid curves on bridges and keep bridges on simple, flat curves when possible. SUPERELEVATION SUPERELEVATION WHAT IS SUPERELEVATION? STANDARD DEFINITION OF SUPER ELEVATION: In simple words, super elevation is the Super elevation is the transverse slope provided to counteract difference in elevation of outer and inner the effect of centrifugal force and reduce the tendency of vehicle edge of road or railway track. to overturn & to skid laterally outwards by raising the pavement of outer edge with respect to inner edge. It is represented by the letter ‘e’.  SUPERELEVATION ADVANTAGES OF PROVIDING SUPER ELEVATION As we all know that tan theta is = opposite side / adjacent side Super elevation is provided to achieve higher Therefore, tan theta = E/B speed of vehicles. Where; It increases the stability of fast-moving vehicles E = super elevation when they pass through a horizontal curve. B = Breadth of road It decreases the stresses on the foundation. In the absence of super elevation on the road along curves potholes are likely to occur at the outer edge of the road. AASHTO recommends the following maximum superelevation rates: Maximum superelevation rates of 4% and 6% are for urban areas. Maximum superelevation rates of 6% and 8% are for areas that have frequent ice and snow. Maximum superelevation rates of 10% and 12% in rural areas without ice or snow concerns.  SUPERELEVATION Design Methods: Centerline Rotation: Most common method where the entire cross-section of the road is rotated about the centerline. Alternative Methods: Includes revolving around the inside or outside edge of the pavement.  SUPERELEVATION Example 1. Consider the radius of a horizontal curve as 100m the design speed is 50 kmph and the coefficient of lateral Common formula to calculate superelevation friction is 0.15. calculate the super elevation. Solution: ; When velocity ‘V’ is in Kmph (kilometer per hour) ; When velocity ‘V’ is in m/sec (meter per second) convert slope value since our slope value 0.047 e = Rate of Superelevation in % 0.047 = 4.7% f = lateral friction factor Conversion Percentage to Ratio: V = velocity of Vehicle in m/s R = radius of circular curve in m Complementary Design: Horizontal and vertical alignment should work together, considering both traffic operation and appearance. Curvature Transition: Vertical curvature should be superimposed on horizontal curvature for a smoother and more pleasing facility. Design Speed Importance: Design speed is crucial for determining alignment and profile, affecting curvature, sight distance, width, clearance, and maximum gradient. Guidelines for Alignment: Balance curvature and grades; avoid steep grades with excessive curvature or flat grades with long grades. Analyze the effects of combined horizontal and vertical curvature on traffic. Avoid sharp horizontal curves at the top of steep vertical crests; lead with horizontal curvature. Introduce only flat horizontal curvature near the bottom of steep grades. Ensure safe passing sections on 2-lane highways take priority over alignment coordination. Keep horizontal and vertical curvature flat at highway intersections. Consider median width variation and separate profiles on divided highways for operational benefits. Design alignments in residential areas to reduce noise and visibility; slight adjustments can enhance buffer zones. Enhance scenic views with alignment design, showcasing natural and manmade features. Preliminary Design Coordination: Start with a comprehensive design using long continuous working drawings for better visualization. Adjustment Process: After preliminary alignment study, make adjustments for desired coordination, checking curvature, gradient, sight distance, and superelevation based on design speed. Superelevation Considerations: Examine how superelevation transitions affect gutter-line profiles, especially on flat grades. Intersection and Driveway Locations: While intersections are key controls, they shouldn't compromise broader alignment goals.  WIDENING Road widening refers to the process of increasing the width of an existing roadway to accommodate more traffic, improve safety, or enhance the overall functionality of the road. This can involve various modifications, such as adding lanes, shoulders, or adjusting curves to better accommodate larger vehicles.  TYPES OF ROAD WIDENING 1. General Widening 2. Lane Widening 3. Extra Widening 4. Shoulder Widening 5. Turn Lane Addition  SPECIFICATIONS OF ROAD WIDENING IN TERMS OF MEASUREMENT 1) Lane Width Standard Lane Width : The typical width for a traffic lane ranges from 3.0 to 3.6 meters. Wider lanes may be specified for high-speed roads or areas with heavy truck traffic. Extra Widening on Curves : For curved sections of the road, additional width may be required. This "extra widening" can vary based on the radius of the curve and the design speed, often calculated using specific formulas to ensure safe vehicle maneuverability.  SPECIFICATIONS OF ROAD WIDENING IN TERMS OF MEASUREMENT 2) Shoulder Width Shoulders are generally required to be at least 1.2 meters wide. This provides space for emergency stops and enhances safety for cyclists and pedestrians.  SPECIFICATIONS OF ROAD WIDENING IN TERMS OF MEASUREMENT 3) Total Road Width The total width of the road after widening will depend on the number of lanes and the width of shoulders. For example, a two-lane road with a shoulder on each side might have a total width of approximately 8.4 to 10.8 meters (considering lane widths and shoulder widths).  SPECIFICATIONS OF ROAD WIDENING IN TERMS OF MEASUREMENT 4) Cross-Slope and Camber The cross-slope of the road surface is typically designed at a gradient of 2% to 3% to facilitate drainage. The camber height may also be specified to ensure proper water runoff, particularly important in areas prone to heavy rainfall.  SPECIFICATIONS OF ROAD WIDENING IN TERMS OF MEASUREMENT 5) Clear Zone Requirements A clear zone, which is the area adjacent to the roadway that is free of obstacles, is often specified to be at least 1.5 to 3.0 meters wide, depending on the road type and speed limit. This area is crucial for safety, allowing vehicles that leave the roadway to recover without hitting fixed objects.  SPECIFICATIONS OF ROAD WIDENING IN TERMS OF MEASUREMENT 6) Vertical Clearance The vertical clearance above the roadway must meet minimum standards, typically around 4.5 meters for highways, to accommodate larger vehicles and ensure safety.  KEY CRITERIA 1. Traffic Volume and Flow 2. Safety Considerations 3. Geometric Design Standards 4. Environmental Impact 5. Community and Stakeholder Engagement 6. Cost-Benefit Analysis 7. Regulatory Compliance 8. Construction Techniques REASONS FOR ROAD WIDENING 1. Improved Safety 2. Increased Capacity 3. Enhanced Traffic Flow 4. Accommodating Larger Vehicles 5. Future-Proofing Infrastructure 6. Mitigating Congestion  CONSIDERATIONS AND CALCULATIONS FOR WIDENING: 1. Current Road Dimensions: Width: Measure the current width of the road. Length: Measure the length of the section to be widened. 2. Desired Width: Determine the new width needed for the road after widening. 3. Right-of-Way: Check if the existing right-of-way is sufficient or if it needs to be expanded.  CONSIDERATIONS AND CALCULATIONS FOR WIDENING: 4. Area Calculation: Calculate the area to be widened using the formula: Area= Length × (New Width−Current Width) 5. Materials Needed: Volume of Material: Depending on the type of material (asphalt, concrete, etc.), calculate the volume required for the widened section. Convert the area into cubic units if needed: Volume=Area×Depth  CONSIDERATIONS AND CALCULATIONS FOR WIDENING: 6. Cost Estimation: Estimate the cost of materials, labor, and any additional expenses (permits, machinery, etc.). 7. Drainage and Utilities: Assess any drainage adjustments and the relocation of utilities that may be impacted by the widening. 8. Environmental Impact: Consider potential environmental impacts and any necessary assessments or permits.  CONSIDERATIONS AND CALCULATIONS FOR WIDENING: 6. Cost Estimation: Estimate the cost of materials, labor, and any additional expenses (permits, machinery, etc.). 7. Drainage and Utilities: Assess any drainage adjustments and the relocation of utilities that may be impacted by the widening. 8. Environmental Impact: Consider potential environmental impacts and any necessary assessments or permits. INTERSECTION & INTERCHANGES AT-GRADE INTERSECTION Two or more roads cross at the same level. GRADE SEPARATED INTERSECTION without ramps Grade-separated intersection (one road passes over another) without ramps to connect them.  INTERCHANGES (Grade Separated Intersection with ramps) It is a system of interconnecting roadways in conjunction with one or more grade separations that provides for the movement of traffic between two or more roadways or highways on different levels.  IMPORTANCE Both intersections and interchanges manage traffic flow and are critical for road connectivity, though interchanges focus more on eliminating direct traffic conflicts through grade separation. GUIDELINES IN DESIGNING AT-GRADE INTERSECTION Provide sight distance at least equal to the stopping distance for the design speed of the road, and preferably more. Avoid placing the intersection where the major road is on a sharp horizontal curve. Intersections where either road is on a steep grade are difficult to design, so avoid them if possible. Where an intersection occurs in fill with the major road considerably higher that the minor road, make certain that the ramps of the minor road begin some distance from the edge of the major road. Make the intersection as nearly right angled as possible.  FACTORS AFFECTING DESIGN HUMAN FACTORS TRAFFIC ENGG. CONSIDERATION Driving habits Classification of each intersecting Ability of drivers to make decisions roadway Driver expectancy Design and actual capacities Decision and reaction times Design-hour turning movements Size and operating characteristics Conformance to natural paths of of vehicle movement Variety of movements, such as Pedestrian use and habits diverging, merging, weaving and Bicycle traffic use and habits crossing Vehicle speeds Bus involvement Crash experience Bicycle movements Pedestrian movements AT-GRADE INTERSECTION  BASIC TYPES OF INTERSECTIONS 1. T-Intersection (Three-Leg): The simplest type, where one road meets another at a right angle, forming a "T" shape. Variations can exist in the angle of approach.  BASIC TYPES OF INTERSECTIONS 2. Four-Leg Intersection: The most common type, where two roads cross at or near right angles, forming four approaches.  BASIC TYPES OF INTERSECTIONS 3. Multi-Leg Intersection: These involve more than four approaches and are typically found in areas with complex road systems.  BASIC TYPES OF INTERSECTIONS 4. Roundabouts: It is an intersection with a central island around which traffic must travel counter-clockwise and in which entering traffic must yield to circulating traffic. Mini-roundabouts Single-lane roundabouts Multilane roundabouts KEY TRAFFIC MANAGEMENT SELECTION CONSIDERATIONS Unsignalized type of intersection KEY TRAFFIC MANAGEMENT SELECTION CONSIDERATIONS Roundabout KEY TRAFFIC MANAGEMENT SELECTION CONSIDERATIONS Signalized type of intersection GRADE SEPARATED INTERSECTION without ramps Grade-separated intersection (one road passes over another) without ramps to connect them.  INTERCHANGES Grade-separated intersection (one road passes over another) with ramps to connect them. FUNCTION 1. To provide separation between two or more traffic arteries. 2 To facilitate the easy transfer of vehicles from one entry to the other or between local roadway and the freeway.  TYPES OF INTERCHANGES 1. Y- Type interchange 2. T or Trumpet interchange Three-Legged Interchange  TYPES OF INTERCHANGES 3. Diamond Interchange 4. Partial Cloverleaf Interchange Four-Legged Interchange  TYPES OF INTERCHANGES 5. Cloverleaf Interchange 6. Directional Interchange Four-Legged Interchange  TYPES OF INTERCHANGES 7. Through freeway with rotary flyover with roundabout  REFERENCES 1. Elements of Roads & Highways by Max b. Fajardo 2. DPWH Design Guidelines, Criteria and Standards, Volume 4 THANK YOU!