4.1 Design of Highways and Railways Flashcards
What are the 11 factors influencing highway design?
- functional classification
- design hourly traffic volume and vehicle mix
- design speed
- design vehicle
- cross section of the highway, such as lanes, shoulders, and medians
- presence of heavy vehicles on steep grades
- topography of the area that the highway traverses
- level of service
- available funds
- safety
- social and environmental factors
Highways are classified according to their functions in terms of ______.
the service they provide
______ facilitates a systematic development of highways and the logical assignment of highway responsibilities among different jurisdictions.
highway functional classification
Highways and streets are categorizes as _____ or ____, depending on the area in which they are located which affects the type of land use and population density, which in turn influences travel patterns.
rural, urban roads
Within the classification of urban and rural, highways are categorized into 5 groups: ____
- principal arterials
- minor arterials
- major collectors
- minor collectors
- local roads and streets
This system of highways serves the major activity centers of the urban area and consists mainly of the central business districts (CBSs) of urbanized area.
urban principal arterial system
What are the 3 subclasses of urban principal arterial system based mainly on the type of access to the facility?
- interstate
- expressways
- other principal arterials
_____, with fully-controlled access and grade separated interchanges.
interstate
____, which have controlled access but may also include at-grade intersections.
expressways
____, with partial or no controlled access.
other principal arterials
Streets and highways that interconnect with and augment the urban primary arterials are classifed as _____.
urban minor arterials
This system serves trips of moderate length and places more emphasis on land access than the primary arterial system.
urban minor arterial system
All arterials not classified as primary are included in this class.
urban minor arterial system
The main purpose of streets within this system is to collect traffic from local streets in residential area or in central business districts (CBDs) and convey it to the arterial system.
urban collector system
Thus, collector streets usually go through residential areas and facilitate traffic circulation within residential, commercial, and industrial areas.
urban collector street system
This system consists of all other street within the urban area that are not included in the three systems described earlier.
urban local street system
The primary purposes of these streets are to provide access to abutting land and to the collector streets.
urban local street system
This system consists of a network of highways that serves most of the interstate trips and a substantial number of intrastate trips.
rural principal arterial system
Virtually all highway trips between urbanized areas and a high percentage of trips between small urban areas with populations of 25,000 or more are made of this system.
rural principal arterial system
The system is further divided into freewars (which are divided highways with fully controlled access and no at-grade intersections), and other principal arterials not classified as freeways.
rural principal arterial system
This system of roads augments the principal arterial system in the formation of a network of roads that connects cities, large towns, and other traffic generators, such as large resorts.
rural minor arterial system
Travel speeds on these roads are relatively high with minimum interference to through movement.
rural minor arterial system
Highways within this system carry traffic primarily within individual conties, and trip distances are usually shorter than those on the arterial roads.
rural collector system
What are the 2 subdivisions of rural collector system?
- rural major collector roads
- rural minor collector roads
Routes under this system carry traffic primarily to and from county seats and large cities that are not directly served by the arterial system.
rural major collector system
The system also carries the main intracountry traffic.
rural major collector system
This system consists of routes that collect traffic from local roads and convey ito to other facilities.
rural minor collector system
One important function of minor collector roads is that they provide linkage between rural hinterland and locally important traffic generators such as small communities.
rural minor collector system
This system consists of all roads within the rural area not classified within the other systems.
rural local roads system
These roads serve trips of relatively short distances and connect adjacent lands with the collector roads.
rural local road system
What are the 5 highway design standards?
- design hourly volume
- design speed
- design vehicle
- cross-section elements
- right of way
____ is the projected hourly volume that is used for design.
design hourly volume
This volume is usually taken as a percentage of the expected ADT on the highway.
design hourly volume
____ is defined as a selected speed to determine the various geometric features of the roadway.
design speed
_____ depends on the functional classification of the highway, the topography of the area in which the highway is located, and the land use of the adjacent area.
design speed
What are the 3 groups topography is generally classified into for highway design?
- level/flat
- rolling
- mountainous terrain
A _______ is selected to represent all vehicles on the highway.
design vehicle
What are 3 characteristics used to establish the design standards of the highway; design vehicle.
- weight
- dimensions
- operating characteristics
The vehicle type is selected as the design vehicle is _______.
the largest that is likely to use the highway with considerable frequency
What are the 3 guidelines apply when selecting a design vehicle?
- when a parking lot or a series of parking lots are the main traffic generators, the passenger car may be used.
- for the design of intersections at local streets and park roads, a single-unit truck may be sued
- at intersections of state highways and city streets that serve buses with relatively few large trucks, a city transit bus may be used.
What are the 3 principal elements of a highway cross section?
- traffic lanes
- shoulders
- medians
______ include median and roadside barriers, curbs, gutters, guard rails, sidewalks, and side slopes.
marginal elements
What are the 7 marginal elements?
- median
- roadside barriers
- curbs
- gutters
- guard rails
- sidewalks
- side slopes
For traffic lanes, on lower trafficked roads, the width can be _____.
reduced
For a single lane road traffic, the lane width is ____.
4.0 m
For a two-lane national road, the minimum width is ______ (total 6.7 m).
2 x 3.35 m
As traffic volume increases, to the need for extra width is justified. This width can increase up to a maximum of _____.
3.65 m
The ____ of a pavement cross section is always contiguous with the traffic lane so as to provide an area along the highway for vehicles to stop when necessary.
shoulder
_____ is desirable for roads carrying over 1,000 ADT.
paving of shoulder
The ____ can accommodate the character of the traffic fleet, the maneuverability of passing needs, emergency parkin, and periodical maintenance of the road.
paved shoulder
A ____ is the section of a dividend highway that separates the lanes in opposing directions.
medians
Medians can either be ____, ____, or ____.
- raise
- flush
- depressed
What are the 7 functions of a median
- providing a recovery area for out-of-control vehicles
- separating opposing traffic
- providing stopping area during emergencies
- providing storage area for left-turning and U-turning vehicles
- providing refuge for pedestrians
- reducing the effect of headlight glare
- providing temporary lanes and cross-overs during maintenance operations
_____ are frequently used in urban arterial streets because they facilitate the control of left-turn at intersections by using part of the median width for left-turn-only lanes.
raised medians
What are the 2 disadvantages of raised medians?
- possible loss of control of the vehicle by the driver if the median is accidentally struck
- they cast a shadow from oncoming headlights, which results in drivers finding it difficult to see the curb.
______ are commonly used on urban arterials.
flush medians
Flush medians can also be used on ____,, but with a median barrier.
freeways
______ are generally used on freeways and are more effective in draining surface water.
depressed medians
A side slope of ____ is suggested for depressed medians, although a slope of ____ may be adequate.
6:1, 4:1
A ____ is defined as a longitudinal system used to prevent an errant vehicle from crossing the portion of a divided highway separating the traveled ways for traffic in opposite directions.
median barrier
_____ protect vehicles from obstacles or slopes on the roadside.
roadside barriers
____ also may be used to shield pedestrians and property from the traffic stream.
roadside barriers
_____ are raised structures made of either Portland cement concrete or bituminous concrete (rolled asphalt curbs).
curbs
Use mainly on urban highways to delineate pavement edges and pedestrian walkways.
curbs
___ also used to control drainage, improve aesthetics, and reduce right of way.
curbs
Curbs can be generally classified as either ____ or ____.
- vertical
- sloping
____ or drainage ditches are usually located on the pavement side of a curb.
gutter
To provide the principal drainage facility for the highway.
gutter
They are sloped to prevent any hazard to traffic.
gutters
Gutters can be design as V-type sections or as ____, ____, ____.
- broad
- flat
- rounded section
Pavements on straight sections of two-lane and multilane highways without medians are sloped from the middle downward to both sides of the highway, resulting in a traverse or cross slope, with a cross section shape that can be ___, ___, or____.
- curved
- plane
- combination of the two
A parabola is generally used for curved cross sections, and the highest point of the pavement (called the crown) is ____, with the cross slope increasing toward the pavement edge.
slightly rounded
____ consists of uniform slopes at both sides of the crown.
plane cross slopes
The ____ has once advantage which is that the slope increases outward to the pavement edge, thereby enhancing the flow of surface water away from the pavement.
curved cross section
A diadvantage is they are difficult is they are difficult to construct.
curved cross section
_____ are provided on embankments and files to provide stability for earthworks.
side slopes
The also serve as a safety feature by providing a recovery area for out-of-control vehicles.
side slopes
What are the 3 important sections of the cross when being considered as a safety feature?
- hinge point
- foreslope
- toe of the slope
The ____ is the total land area acquired for the construction of a highway.
right of way
The width should be sufficient to accommodate for all the elements of the highway cross section, any planned widening of the highway, and public-utility facilities that will be installed along the highway.
right of way
