HIGHWAY Q2

Modules 4-6

Highway Design

Geometric + Structural

AASHTO (American Association of State Highway and Transportation Officials)

• Is a non-profit association representing highway and transportation departments in the 50 states of America, the District of Columbia and Puerto Rico

• Its primary goal is to foster the development, operation and maintenance of an integrated national transportation system.

Clear information and guidance through a variety of road signs & Avoiding abrupt changes in the traffic as well as the road standards

Drivers expect highway agency to provide them with:

BASIC CONSIDERATIONS ON GEOMETRIC DESIGN OF HIGHWAYS

 Must be suitable for the traffic volume

 Must be consistent and mist avoid surprise changes in alignment, grade and distance

 Must be pleasing to the user and those who live along with it

 Must be complete

 Should be as simple as possible from the standpoint of the builder

 Should be maintained at the least cost

 Must be safe

Road Network

Composed of various types of roads, each of which performs a particular service in facilitating vehicular travel between points of trip origin and destination.

Consideration for Classification

• Legal control

• surface type

• function

• geometric elements

• location

• traffic volume

Urban Roads

• Principal arterial/ freeways/ expressway

• Minor Arterial

• Collector Street

• Local Street

Rural Roads

• Principal arterial/ freeways/ expressway

• Major and Minor Arterial

• Collector Street

• Local Street

Freeways

Through movement exclusively

Surface Arterials

Through movement primary and some live accessCol

Collectors

Traffic movement to higher rank roads, access to abutting properties

Local Roads

Access to abutting land and local traffic movement

Philippine Road System

• National Road

• Provincial Road

• City Road

• Municipal Road

• Barangay Road

• Tourism Road

• Farm to Market Road

Highway Capacity

• Maximum number of vehicles that are reasonably expected to pass a given point over a given number of time

• Measured in terms of number of vehicles per hour (veh/hr)

• As. the volume of traffic approaches capacity, the average speed is markedly reduced

• Depends on the average length of vehicles and the average spacing of moving vehicles which depends on the reaction time of the driver

Reaction Time

period of time that elapsed before muscular reaction occurs

Perception Time

interval of time required before reaction begins

Perception time + reaction time=

2.5 seconds

Highway Capacity

v/s (where s=v(t), t=2.5s then + overall length of design vehicle)

Design Hourly Volume (one way)

ADT (planned traffic) x K/100

Design Hourly Volume (two way)

ADT (planned traffic) x K/100 x D/100

DHV as a percentage of ADT for different types of roads as recommended by AASHTO:

• Rural roads – 15%

• Recreational roads – 35%

• Urban roads – 8%

Design Speed

• The speed determined for design and correlation of the physical feature of a highway that influences vehicles operation

• It is the maximum speed that can be maintained over a specified section of the highway when weather and traffic conditions are so favorable that the design features (tightness and super elevation of curves, sight distance, and grade) of the highway govern

• Selected to achieve a desired level of operation and safety on the highway

Level

• Relatively flat

• Horizontal and vertical sight distance are generally long and can be achieved without much construction difficulty or major expenses

Rolling

•Natural slopes that often rise above and fall below the highway grade with occasional steep slopes that restrict the normal vertical and horizontal alignments

Mountainous

•Sudden changes in ground elevation in both the longitude and transverse directions

•Requires hillside excavations to achieve acceptable horizontal and vertical alignment

Design Vehicles

• Used to determine critical design features such as radii at intersections and turning roadways as well as highway grades

• Passenger cars, trucks, trailers, buses, motorcycles, etc.

Principal Elements

•Pavement

•Travel lanes

•Shoulders

• Median

Marginal Elements

•Curbs

•Sidewalks

•Drainage channels and side slopes

•Traffic barriers

•Frontage roads

•Noise control

•Roadside control

•Pedestrian crossings

•Curb-cut ramps

•Bicycle facilities

•Bius turn outs

•Park and ride facilities

Traffic Lane

portion of the pavement allotted for the use of single line of vehicles

Cross Slope

• slope of the surface of a pavement measured at right angles to the horizontal alignment

• Steeper slope are strongly recommended to flow rainwater away more rapidly reducing the water thickness on the road pavement

TRAFFIC LANE / TRAVEL LANE

• Widths usually vary from 2.7m to 3.6m

• 3 or 3.3m – on 2-lane, 2-way rural roads / low speed facilities

• 2.7m on low traffic urban areas with extreme right-of-way concerns

• DESIRABLE WIDTH IS 3.65 meters.

• All roads should be designed to accommodate trucks, buses and passenger cars with safety and convenience

• Minimum width of traffic lane depends upon the width of the design vehicle and upon the lateral clearance between passing vehicles and clearances from abutments or overpasses or from curbs and gutter

Total Width of the highway

= 𝑠𝑢𝑚 𝑜𝑓 𝑡ℎ𝑒 𝑤𝑖𝑑𝑡ℎ 𝑜𝑓 𝑡ℎ𝑒 𝑡𝑟𝑎𝑓𝑓𝑖𝑐 𝑙𝑎𝑛𝑒𝑠 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 + 𝑖𝑠𝑙𝑎𝑛𝑑𝑠 + 𝑐𝑢𝑟𝑏𝑠 𝑎𝑛𝑑 𝑔𝑢𝑡𝑡𝑒𝑟𝑠 + 𝑠ℎ𝑜𝑢𝑙𝑑𝑒𝑟𝑠 𝑜𝑟 𝑤𝑎𝑙𝑘𝑤𝑎𝑦𝑠 + 𝑑𝑖𝑡𝑐ℎ𝑒𝑠 𝑜𝑟 𝑑𝑟𝑎𝑖𝑛𝑠 𝑎𝑛𝑑 𝑜𝑡ℎ𝑒𝑟 𝑓𝑒𝑎𝑡𝑢𝑟𝑒

Shoulder

• Minimum Width – 1.0 m (DPWH Manual)

• Minimum width of 1.5 m for AADT greater than 1250

• No difference in elevation between surface of the shoulder and the surface of the pavement

Median

section of a divided highway that separates the lanes in opposing directions

Functions of Median

• To separate opposing traffic streams

• To prevent U-turn and enhance the safety to traffic flow

• Makes turning of vehicles smooth and safe operation

• To provide space to install traffic signs or other traffic managing facilities

• To provide storage lane for left turn vehicles at the intersections

• To provide a haven in case of emergency

• To minimize headlight glare in night time

• Reduces conflicts and accidents between opposing streams of traffic

Width of mediam shoulder

Flexible

undergo a dynamic deflection upon impact and generally impose lower impact forces

semi rigid

Rigid

Crash Cushion

Grade Line

• the longitudinal profile of the highway as a measure how the centerline of the highway rises and fall

• it affects the performance or speed of a vehicle

• it appears on a profile taken along the road centerline

• it is a series of straight lines connected by parabolic vertical curves to which straight grades are tangent

Curb

• Raised structures that are used mainly to delineate pavement edges and pedestrian walks

• Used to control drainage, improve aesthetics and reduce right of way

Purpose of Curb

• drainage control

• Roadway edge delineation

• Road of way reduction

• Aesthetic

• Delineation of pedestrian walkways

Sidewalk

Wherever roadside and land development conditions affect regular pedestrian movement along a highway, a sidewalk or path suitable to the conditions should be provided.

Sidewalk

• Widths in lower speed residential areas may vary from 1.2 to 2.4 meters.

• A good minimum width for a sidewalk that allows two people to pass is 1.8 meters.

• less than 1.5 m wide require the addition of a passing section every 60m for accessibility

  • for pedestrian access to schools, parks, shopping areas, and transit stops and sidewalks in commercial areas should be provided along side of the street.

Drainage Channel

perform the important function of collecting water and conveying surface water

Open channel ditches

most economical drainage channe

Side Slopes

should be designed to enhance roadway stability and provide a reasonable opportunity for recovery for an out of control vehicle

Drainage Channel

• perform the important function of collecting and conveying surface water from the highway right-of-way

• Should have adequate capacity for the design runoff, provide for unusual stormwater with minimum damage to the highway and be located and shaped to provide a smooth transition from the roadway to the back slope

• The most economical method of constructing a roadside channel usually entails the formation of open-channel ditches by cutting into the natural roadside terrain

• Desirable grade of channels depend on the velocity of flow

Frontage Roads

-Roads used to control access to nearby arterial highways, while also functioning as a street facility serving adjoining properties and maintaining traffic circulation on each side of the arterial

-Segregates local traffic from higher speed through traffic and intercept driveways of residences and commercial properties along the highway

• outer separation” - the area between the through traffic on the arterial and the local traffic on the frontage road

Noise Barrier

Used to an increasing extent in recognition of the adverse effect that noise can have on people living on, working on, or otherwise using land adjacent to highwayR

Roadside Control

• Used by highway authorities to keep the full width of right-of-way unaffected for public highway purposes

• Used to minimize interference to through traffic movement

Tunnel

• Long, narrow terrain ridges where a cut section may be either costly or have environmental consequences

• Narrow rights of way where all of the surface area is needed for street purposes

• Large intersection areas or a series of intersections on an irregular or diagonal pattern

• Railroad yards, airport runways, or similar facilities

• Existing or planned parks or similar land uses

• Locations where right-of-way acquisition costs exceed the cost of tunnel construction and operation

Pedestrian Crossing

• safe access to all destinations that are accessible to motorists, plus they will want to access to other destinations that are not accessible to motorists such as trails and parks

• must be able to cross streets and highways at regular intervals. Unlike motor vehicles, pedestrians cannot be expected to go far out of their wat to take advantage of a controlled intersection.

Marked crossings

• are not only used to advice pedestrians where to cross the street but also send a message to motorists that they are in, or approaching, a pedestrian area

• The width is 4 meters

Raised Crosswalks

• are typically used at midblock locations to serve not only as a visual element for motorists, but also to slow traffic speeds

Pedestrian refuge

allows pedestrians to cross one direction of traffic at a time

Curb-Cut ramps

• These are needed to accommodate persons of disabilities

• These are necessary to provide access between the sidewalk and the street at pedestrian crossing

• The minimum curb ramp width should be 0.9m, the maximum curb ramp grade should be 6% and the maximum cross slope on a sidewalk should be no more than 2%.

bikeway min width

1.22m

how many bikes per hour in one way?

1275 bikes

how many bikes per hour in two way?

1900 bikes

Bike speedway

11 to 24 kph

CLASS I BICYCLE FACILITY : BIKE PATH OR TRAIL

completely separated roadway designed for the exclusive use of bicycles; typically separated by open space or barrier

CLASS II BICYCLE FACILITY : BIKE LANE

a portion of the roadway, which has been designated for exclusive use by bicycle normally distinguished by a paint stripe, curb or barrier

CLASS III BICYCLE FACILITY : SHARED ROADWAY OR BIKE ROUTE

a roadway that has been officially designated and marked as bicycle route but which is used both by motor vehicle and bicycle traffic

Bus turnout length

min of 60m and max of 185m

bus min width

3.6m

bus turnout thickness for asphalt

at least 100mmbus t

bus turnout thickness for concrete

230mm

Intersection

It is the general area where two or more highways join or cross, within which are included the roadway and roadside facilities for traffic movements in that area

At-grade intersection

• Intersection area is part of every connecting road or street

• in which traffic is directed into definite paths is called channelized intersection

• Can be 3-leg, 4-leg or multi-leg

Roundabout

• intersection with a center island around which traffic must travel counterclockwise and in which entering traffic must yield to circulating traffic

  • may be mini, single-lane or multi lane roundabout

Interchange

A system of interconnecting roadway in conjunction with one or more highway separations providing for the interchange of traffic between two or more intersecting highways, usually without at-grade crossings of through and major turning movements

Main line

track constantly used for train operation

Sliding

track other than a main line

Track gauge

shortest distance between inner side surface of two rail heads of a track measured

Station

place used by passengers to get in and out of trains or for the loading and unloading of cargo

Signalling yard

place mainly used for mutual passing or waiting for a train

Shunting yard

palce mainly used for the shunting of rolling stock or the composition of a trainD

Depot

place mainly used to accommodate and maintain rolling stock

Train

a group of rolling stock composed for operation on track outside a station

Rolling stock

locomotive, passenger cars , freight cars and special-purpose cars

operation safety device

signalling safety devices, level crossing safety devices and safety communication devices

Signalling safety devices

devices to display railway signals and devices to automatically reduce the train speed or stop a train, etc. in accordance with the signal indication in order to ensure the safe operation of a train, etc

Signals

objects indicating the operating conditions of a train, etc. to railway staf

Signs

physical movement and so forth to mutually indicate intentions between railway staf

Markers

objects indicating the position, direction and conditions, etc. of specific items to railway staff

Gauge and Slack

• The gauge shall be decided to ensure the smooth running of rolling stock, taking the structure of vehicles and others into consideration.

• At curves, appropriate slack shall be provided in accordance with the curve passing performance of rolling stock

Curve Radius

shall be adopted based on the standard minimum curve radius to ensure the smooth running of rolling stock, taking the curve passing performance and running speed of vehicles and the cant, etc. into consideration.

Cant

A circular curve shall be provided with cant in accordance with the gauge, radius of curve and speed of rolling stock, etc. It must be ensured that the largest value of the cant will not adversely affect the stability, etc. of rolling stock which is either travelling at a low speed or which is stationary.

Transition Curve

shall be provided between a straight line and a circular curve or between two circular curves depending on the structure, degree of cant and travelling speed of rolling stock, etc.

Grade

shall be determined in consideration of the power performance, braking performance and speed of operation, etc. of rolling stock and the standard steepest grade for main lines is given below.

Vertical Curve

In places where the grade changes, a vertical curve shall be introduced to prevent the derailing of rolling stock and to prevent any unpleasant feeling on the part of passengers, taking the speed of train operation and rolling stock performance, etc. into consideration

Construction Gauge

shall be determined to ensure the safety of rolling stock and passengers, etc. vis-a-vis the pitching or rolling, etc. of travelling rolling stock and no structure shall be introduced within the construction gauge.

Width of formation level

shall be determined to ensure the safety of passengers and workers, etc. in consideration of the pitching motion of travelling rolling stock and the track structure, etc

center-to-center distance of adjacent tracks

shall be determined by adding a margin to the width of rolling stock in consideration of pitching motion to ensure its safety and of the passengers. This distance shall be widened at curves, etc. in response to the expected swaying, etc. of rolling stock.

track and civil engineering structure

shall be determined to ensure the safety and security of the rolling stock and railway facilities in consideration of the structure of rolling stock, train weight and sub-grade conditions, etc.

building construction

shall be constructed so as not to compromise the safety of the rolling stock and passengers

disaster prevention devices, safety devices and evacuation devices

shall be installed to avoid entry of unwanted persons and of falling objects onto the tracks. Similarly, measures shall be applied to prevent damage to the facilities which may be brought about by accidents or any untoward incidents happening in the perimeter area.

Station Facilities

• effective track length, platform length/width, etc. shall be determined so as to ensure smooth train operation with consideration for passenger safety

• Smooth transfers between railway line

• Smooth transfers between railway and road-based and other modes of transport