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1.1 Definition of horizontal alignment? Elements used to determine horizontal alignment of highway segments: names & illustrative figures 3.1Horizontal alignment: Definition, geometric components, and various types of points along horizontal alignment? 3.2 Horizontal alignment: Definition and fundamental principles on geometric design? Definition: Horizontal alignment of a highway represents the projection of its facilities on a horizontal plane while generally consisting of straight-line segments (or horizontal tangents) connected by curves (including circular or compound curves) Design principles: Based on balance between Economy-Engineering-Environment - Minimum ratio of total design length to beeline (length as the crow flies) - Direction of segments should not be East – West; should not be perpendicular to the direction of wind force - All design criteria regulated for the given category must be satisfied - Harmony with main features of geography, topography, geology, and etc to minimize filling or excavation quantities and environmental impacts - Combine human factors with the design - Geometric design values should be as far from critical values as possible to maximize safety, comfort, and economy - Horizontal alignment of a highway must be designed in conjunction with both vertical alignment and cross-sections - Avoid environmental reservations and apply engineering countermeasures for environmental protection & minimization of negative impacts - Carefully examine intersections with railways, river-ways, or the other highways of higher categories Points along segment: + First & end points + Main points of curves + Points of station location + Topographical points + Points of works + Auxiliary points Geometric elements of horizontal alignment: -Straight-line segments: there are attributes: +First point and orientation angle +Point and angle of diversion +Length of horizontal tangent -Circular curves: there are attributes: +Angle of diversion +Circular curves radius -Curves have radius change (connecting curve), there are attributes: form of curve and length of connecting curve 1.2 Definition of vertical alignment, red & black vertical alignments? Elements used to determine red vertical alignment: names & illustrative figures? Definition Vertical alignment of a rural or urban highway, which is referred to as a geometry represented by the grade line or longitudinal section in the vertical plane, consists of tangent grades and vertical curves Existing vertical alignment is the longitudinal expression of changes in existing altitudes with respect to its stations, which is informally called “black line” in practical Designed vertical alignment is the longitudinal expression of changes in designed altitudes with respect to the same stations, which is informally called “red line” Elements used to determine red vertical alignment: +Red vertical landmark’s altitude at the beginning of the line +Longitudinal grade (id) % and the slopes length +Vertical curved line where the slope is changed The design of the vertical alignment therefore involves the selection of suitable grades for the tangent sections and the appropriate length of vertical curves 1.3 Definition of cross sections? Elements of highway cross sections: names, definitions & illustrative figures? Definition Cross section is used to define the configuration of a proposed roadway at right angles to the centerline, which has got typical sections showing the width, thickness and descriptions of the pavement section, as well as the geometrics of the graded roadbed, side ditches, and side slopes between right of way limits Elements of highway cross sections A cross section commonly consists of traveled way including: +Driving lanes +Auxiliary driving lanes +Shoulder including soil shoulders and reinforced shoulders +Slopes on the roadsides including fore slopes and back slopes +Ditches including roadside ditches and summit ditches +Curb +Gutters +Boulevards +Sidewalks * Traveled way of a certain rural or urban highway is indicated by lane widths and number of lanes The number of lanes depends on peak-hour traffic volume, specifically design hour volume (DHV), usability efficiency of traffic capacity, and maximum traffic capacity * Shoulder is the portion of the roadway continuous with the traveled way that accommodates stopped vehicles, emergency use, and lateral support of sub-base, base, and surface course; and that can accommodate bicyclists in some cases 2.1 Forces acting on moving vehicles: names & equations? 2.2 Braking distance: definition & establishment of braking distance? Definition Braking distance is counted from the moment when brakes take effect to the moment when the vehicle reaches its required final speed However, it is impossible to execute braking maneuver within a theoretical braking distance because the wheels may stop rotaling and start skidding if the brakes are taken at the remarkable high magnitude, especially on wet pavement surfaces Furthermore, the front wheels will be out of control and the rear wheels will transversally skid when they are all completely braked Therefore, practical braking distance must be greater than theoretical braking one by applying braking coefficient Establishment of braking distance -When brakes take effect on wheels, friction-band effect to rim of wheel, then create braking Moment Mh and braking Force Ph -Braking Force Ph just effect when grip force between wheel & road-surface is enough Otherwise wheels still slips on the road-surface although wheels not turn round So, the maximum useful braking force equals to maximum grip force: Ph = Tmax = φ Gh Tmax: The maximum grip force between wheels and road-surface φ : Coefficient of grip the road Gh: Braking weight -Effectiveness of resistant forces: ∑Phãm = Ph + Pi = φG ± iG Pi: Braking force by slope i: Road’s slope -V1 and V2 are the auto’s speeds before and after braking (km/h) -v1 and v2 are the auto’s speeds before and after braking (m/s) -Braking distance (Sh) when based on conservation on conservation of energy: -Braking distance: k=1,2 :with small auto k=1,3-1,4:with truck and bus - For complete stop (V2=0) 2.3 Definition of sight distance? Applications Definition Sight distances is the continuous length of roadway ahead that is visible to drivers in both horizontal and vertical planes, which exists for safe and efficient operation of rural and urban highways Applications All circumstances such as: determine horizontal clearance to obstructions, vertical curve radius, clearance zone to a railway, etc Stopping sight distance – Dead obstacles Stopping sight distance in front of a stationary obstacle is determined when based on the traffic circumstance in which a given vehicle driven at the design speed must stop safely before it hits a stationary on its lane S1 lpu Sh l0 lpu (brake reaction distance) = v*t [m], in which - v is the design speed [m/s] - t is the interval from the instant that the driver recognizes the existence of an obstacle on the roadway ahead to the instant that the driver actually applies the brakes Sh (braking distance) is the distance that the vehicle travels during the brake is applied S1 (stopping sight distance) V: design speed [km/h] φ: frictional coefficient Obstacle: 0.1m high t: brake reaction time [s] i: longitudinal grade Driver’s eye: m high k: brake coefficient lo: spare (safe) distance = ÷ 10 [m] Stopping sight distance-Live obstacles Vertical curve Purpose: -Ensure the calculate sight distance -Vertical alignment don't kink - To safety, smoothly for vehicle Compulsory application situations:  idesign = /i1 – i2/  2% => Vdesign < 60 km/h  1% => Vdesign  60 km/h Principles of design: -The higher radii the better - Requirements on sight distances and limitation of centrifugal force + Ensure day-time sight distance of crest curves Vertical alignment Requirement& principles of vertical alignment design: Only apply critical values of design criteria in the most difficult circumstances - Minimize number of grade changes and apply lower grades (if possible) - Make the design suitable to main topographic features=>minimize filling or excavation quantities - Combine with design of horizontal alignment and cross-sections=>satisfy requirements on optics and aesthetics - Ensure conditions to drain off surface water and or lower groundwater level - Make the roadbeds be operated under optimal hydrothermal mechanisms - Satisfy design elevations of control points - Improve operation conditions & optimize operation costs - Make the design available to construction, maintenance and repair technologies =>Satisfy design elevations of control points: - Fixed design elevations belong to control points including beginning points, ending points, intersection with railways or highways of higher categories, and etc - Minimum design elevations:+ Areas of permanent surface water: Hv ≥ HMNTX + 0.5 m + Segments on riverbank leading to a bridge:Hv ≥ HSV(P%) + 0.5 m - Minimum design elevations: + Embankments on circular culverts: hđ ≥ 0.5 m or hađ + Segments over groundwater: HĐ ≥ HMNNTT + (0.3-1.2)m + Segments over short bridges: Hmc ≥ HMNTK(P%) + t + k With: hđ = thickness of filling layer on the top of circular culverts hađ = total thickness of pavement structure Hmc = elevation of bridge pavement surface HMNTK(P%) = maximum design water level corresponding to hydrology frequency of P percent t = vertical clearance under bridges k = total structural height of superstructure of bridges HT = elevation of centerline Hv = elevation of outer edge of shoulder HĐ = elevation of bottom of pavement structure MNTT = frequent surface water level MNNTT= calculating ground water level Methodologies of vertical alignment: -Methodologies of vertical alignment base on elements: Engineering, Economy Environment -There are methodologies: +Excavation methodology +Filling methodology Execution steps: -There are steps: Determine design elevations of control points Apply filling or excavation methodology to design “red line” that satisfies allthe requirements mentioned above +Determine grade-changed areas having the following features: - Suitable to main topographic features minimize filling and excavation quantities - Harmonic with the horizontal alignment and cross-sections - Satisfactory to requirements on tangent length: Lmin ≤ LDesign ≤ LMax - Satisfactory to requirements on design grades: imin ≤ iDesign ≤ iMax + Extend two adjacent tangents to determine point of intersection then install a vertical curve Climbing lane Functions -Climbing lane is an “extra” lane that’s used for short distances in certain areas to improve safety, ease congestion and prevent delays These lanes help facilitate the passing of trucks and slow moving vehicles whose speed drops because of the sustained steep grades - In the road which has many trucks, truck-climbing lanes need to be arranged at position where has a big slope to limit the obstruction of truck with cars -Climbing lane allow slower travel for large vehicles, such as large trucks or Semi-trailer trucks, up a steep grade Since heading uphill is difficult for these types of vehicles, they can travel in the climbing lane without slowing traffic behind them -Climbing lanes typically are marked with signage advising slower traffic to keep right Application Only arrange climbing lane when circulation meets the necessary conditions as: + Climbing traffic volume > 200 vehicles per hour +Percentage of trucks or lorries >10% =20 vehicles per hou + id ≥ 4% and Ld ≥ 800m After economic & engineering comparison with grade lowering Compositions -The width of climbing lanes is 3.5 m, in hard case for reducing to 3.0 m -Climbing lane should be a independent route, if not it must be located on paved shoulder -The transition to the side lane is set up toward the start point 35 m and gradually expanded as wedge with the expand rate 1:10 The transition from side lane to main one is also connected as wedge from the peak with the shrinkage 1:20 Speed change lane Functions Speed-Change Lanes are located at entrance or exit positions of intersection with another highway of different categories It will help drivers to avoid changing speed suddenly Applications When the vehicle from the road which has low speed design to one has high speed design, acceleration lane should be arranged In contrast, we have deceleration lane Compositions Compositions of a speed-change lane pursuant to TCVN 4054-2005 (id ≤ 2%).Acceleration lane: Deceleration lane: 3.3 Horizontal curves: compulsory applications, principles on choosing design radii, and compulsory cases when transition curves must be installed? Compulsory applications when velocity design < 60km/h or delta (alpha) ≤ degrees Principles on choosing design radii of horizontal curves + R design ≥ R        + Harmony with topographical features to reduce filling and excavation quantities + Design radius is as high as possible + Sufficient length of arc to install super elevation transition and curve widening + Sufficient length of straight-line segment between two adjacent curves + Ratio of radii: Ri/ Ri+1 ≤ + Connection between adjacent curves: m ≥ (Li + Li+1)/2 + Requirements on aesthetic and optical harmony and spatial combination Compulsory to install transitioned curves - When V design ≤ 60 km/h (TCVN 4054 – 2005) or V design ≤ 60 km/h (22TCN 273 – 2001) 3.4 Lateral clearance design: requirements on geometric design to ensure sight distance on horizontal curves? Rotation around center line Excution steps -First step: A to B make the cross slope of outside edge of roadbed to same the cross slope of outside edge of traveled way -Second step: B to C make all cross slope of outside lane to zero -Third step: C to D make the cross lope of outside lane to the same the cross slope of inside edge of traveled way -Fourth step: make all cross lope to the same the cross slope of inside edge of roadbed -Fifth step: D to E lower elevation of inside edge of traveled way and rise elevation of outside edge of roadbed until set design rate of super elevation  In the method design altitude of center line not be changed but altitude of inside edge of traveled way at the end of transition curve will be down compared altitude of inside edge of traveled way at the beginning transition curve Rotation around inside edge of traveled way Excution steps: -First step: A to B make the cross slope of outside edge of roadbed to same the cross slope of outside edge of traveled way -Second step: B to C make all cross slope of outside lane to zero -Third step; C to D make the cross lope of outside lane to the same the cross slope of inside edge of traveled way -Fourth step: make all cross lope to same the cross slope of inside edge of roadbed -Fifth step: D to E rise the elevation of outside edge of roadbed until set the design rate of super elevation  In this method altitude of inside edge of traveled way not be changed but altitude of center line at the end of transition curve is higher than altitude of center line at the beginning of transition curve Curve widening Purpose: To ensure the conditions of the car run on the curve equivalent as a straight road In the small radius curves need to expand the part for the car to run Because: "when the car runs from the straight road into the circular curve: + Rear wheels off-track with respect to front wheels + Rear axle always off-track towards center of the curve + Front wheels rotate corresponding to turning angle => Vehicles deviate from centerline of the Widening arrangement • The widening section connecting is arranged coincide with the super elevation section connecting or the transition curves When don’t have the elements=> The widening section connecting is arranged : - The half located at the straight line and the half located at the curve - In the section connecting, have to widen even, widen 1m /10m of the length - The curve widening arranges on both outside & inside of curves But on the difficult case, maybe arrange on outside or inside of curves - The number of the curve widening have to calculate: En = (4K3- 3K4 ).E - The direction of the curve widening is the direction of the normal of the center of the carriage-way The curve widening located at the reinforcement hinge The land have to locate at the right of the curve widening Ensure the soid shoulder remaining at least 0.5m - The special vehicle have the number of the curve widening other Tính toán:  With: -La: distance of rear wheels and front wheels -R: the radius of the curves (R ≤ 250 m-TCVN 4054-2005) -V: the velocity of the car -e: the curve widening - Curve widening of a segment with n lanes: E = n.e - Positions of curve widening: + On both outside & inside of curves + On outside or inside of curves - Requirement on curves after being widened: Bsoil shoulder ≥ 0.5 m - Curve widening transition: + in case of compound curve: Le ≡ Lct ≡ Lsc In case of transitio ned curves In case of un-transitioned curves Super elevation Definition:-“Super elevation is the tilting of pavement surface at cross-sections of a curve segment restricted by smaller radii, which counteracts centripetal force for vehicular motions of safety and comfort” -“Rate of super elevation is the slope to which a highway cross-section is tiltedand equals the tangent of baking angle (Effects) Purposes of super elevation: + Mechanical purpose: Reduce lateral resultant force (counteract centripetal force) + Psychological purpose: Make motorists feel safe to drive at Voperation ≥ Vdesign + Aesthetic & optical purposes: make pavement breadth of curves segments with restricted radii not seem smaller than in reality Vertical alignment Definition: is longitudinal section "stretch out",(vertical scale is 10 times as much as longitudinal scale) and longitudinal expression of changes in existing and design altitudes How are highways classified according to their functions? STT Classification Function National Highway Connecting: from Capital to Provincial Central; at least Provincial Centrals; from International Maritime Ports, International Airports to International or major border gates Or extremely important Roads for economy development of areas Provincial Highway Connecting from Provincial Central to District Centrals or Neighboring Provincial Centrals Or extremely important roads for economy development of provinces District road Connecting from District Central to Community centrals of neighboring district centrals Or extremely important roads for economy development of Districts Community road Connecting from Community Centrals to lower level Centrals Or extremely important roads for economy development of Community Urban road Roads in urban areas Special-purpose road Roads serving for transport of one or more institutions How are highways classified according to the design purpose? Please detail classification of conventional highways for design purpose? Classification: - Expressways - Conventional roads - Urban road - Rural road Road class Design Traffic Volume (PCU) Road functions Expressway >25 000 Major Arterial – follows TCVN 5729 : 1997 Major Arterial connecting main national economical, political, Class I >15 000 cultural centers Major Arterial connecting main national economical, political, Class II >6 000 cultural centers Major Arterial connecting main national or local economical, Class III >3 000 political, cultural centers Roads connecting local/ residentical centers National Class IV > 500 Highway Class V >200 Local roads Class VI