HIGHWAYYYY MIDTERM
For economic reasons, the Geometric Features of certain road sections are designed for speed from -----------------------------
30 to 50 kilometers per hour.
References
are made in these books and periodic manuals.
the motorist are being alert and inform that they are approaching sharp curves or blind curves.
by reducing the super elevation combined with easement curves, delineators, striping signs and rumble strips, how can it affect the moterist?
Two Lane Rural Highways Collector Roadway Local Rural Roadway Urban Roadway
cross-section of a typical highway
80-110 km/hr
design speed in rural arterial
105-95 km/hr (mountainous)
design speed in rural freeway
32-48 km/hr
design speed in rural local
64-95 km/hr but 48km/hr in built up area
design speed in urban arterial
48 km/hr
design speed in urban collectors
80-95 km/hr.
design speed in urban freeway
4.80 to 5.40 meters
due to the increased number of vehicles using the roadway, the width was adjusted to -----------
The cloverleaf
type interchange is recommended for freeway and arterial intersections. Intersecting arteries are separated and free of intersections.
"The speed determined for design and correlation of the physical feature of a highway that influence 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 of the highway govern."
AASHTO defined Design Speed as
authoritative
AASHTO publications are -----------
1. Transportation Materials Specification and Tests. 2. Specifications for highway bridges 3. Geometric design standards. 4. Numerous policy statements and guides.
AASHTO publications includes:
"The design speed be set to the greatest degree possible, to satisfy the needs of nearly all drivers both today and throughout the road anticipated life."
AASHTO recommend that:
strong enough to support vehicles.
AASHTO requires that its usable pavement width shall be -------------
no difference
Accident records showed --------- between the 6.60 meters and the 7.20 meters wide pavement.
costly
Acquisition of land for the right of way is very -----
Slope
usually falls in both directions from the centerline of the two-lane highway except where superelevation of curves directs all water towards the inside.
18% less
A 7.20 meters wide pavement has --------- accident compared with pavement narrower than 5.50 m. wide
4%
A 7.20 meters wide pavement has------ fewer accidents than the 6.00 meters wide roadway
G.M. Barriers.
A high non-mountain sloped face concrete barriers called New Jersey. It is cast or extruded in place or precast in section and set in position by crane.
ASSHO
was established on 1914 as an association of State Territorial and District of Columbia Highway Department, and the Federal Highway Administration
2.40 to 3.00 meters
For six or more lanes, ---------- shoulder width is recommended
tightness and superelevation of curves, the sight distance, and grade
Basic Design Feature refers to the ----------------------------------------
Collector Roadway
CROSS SECTION OF TYPICAL HIGHWAY with 6.00 meters wide surface is acceptable only for low volume traffic including few trucks traveling thereon.
Two Lane Rural Highways
CROSS SECTION OF TYPICAL HIGHWAY with a 7.20 meters wide surface is required for safe clearance between commercial vehicles and is recommended for main highways.
Urban Roadway
CROSS SECTION OF TYPICAL HIGHWAY with the minimum design width is 3.60 meters although 3.00 meters is allowed where space is limited.
Local Rural Roadway
CROSS SECTION OF TYPICAL HIGHWAY with the minimum surface width is 4.80 meters for a 30 km / hr. design speed.
Super elevation run off
Curved sections of roadways are usually super elevated
decreases by 30%; 20%
For the 6.00 m., 6.60 m. and,7.20 meters wide pavement with 2.70 to 3.00 m. wide shoulder, recorded accident ------------------ compared to 0 to .60 m. wide shoulder. And ------- compared with a .90 to 1.20 meters wide shoulder
1. Clear information and guidance through a variety of road signs. 2. Avoiding abrupt changes in the traffic as well as the road standards.
Drivers expect the highway agency to provide them with:
1:2 ratios.
Earth fill of normal height is safe on a slope of -------
Highway Practice
Engineering activities, were implemented by the standing committees with the task of preparing specifications manual and standards, representing the current highway engineering practice.
2.40 meters
For ADT's over 2000, -------- wide shoulderis recommended.
◼ 1. Provide deterring devices. ◼ 2. Provide non-traversable energy absorbing barriers. ◼ 3. Provide non-traversable rigid barriers. ◼ 4. Provide G.M. barriers.
For Narrow Median, there are four means of reducing cross median accidents:
60 centimeters
For Rural Collectors Roadway, =--------- wide graded shoulder is required for ADT's less than 400
For a low-volume traffic facilities, modification of the features like the shoulders width in rough areas are usually employed to reduce costs.
For a ------------------- , modification of the features like the shoulders width in rough areas are usually employed to reduce costs.
4% to 6%; 7%
For a gravel shoulder, ----- slope is satisfactory, and ---- slope is effective drainage for turf (grass) surfaces
1.20 meters; 2.40 meters
For arterials with ADT less than 400 the usable shoulder width is fixed at -----------, although ---------- wide is much preferred.
1% to 2%.
For high type pavement, the crown or slope is often -----
18.00 meters
For rural and urban arterials, -------- median or wider is preferred because it allows the use of independent profiles and at the same time minimizes cross over accident.
Highway design usually adopted cross section that is uniform in thickness from end to end of the pavement. This is acceptable on high-volume traffic road facilities.
Highway design usually adopted cross section that is ----------------------------. This is acceptable on -------- traffic road facilities.
3.00 meters wide or 3.60 meters
If there are 6 or more lanes, the median shoulder should be -------------- if truck volume in the design hour exceeds 250.
◼ Road shoulder serves as a place for vehicles to stop when disabled or for some ot her purposes. Road shoulder considerably reduces road accidents. ◼ The road capacity is decreased, and accident opportunity increases if the shoulder is too narrow or omitted in the design. ◼ Shoulder should be continuous along the full length of the roadway. It also adds structural strength to the road pavement. ◼ Shoulder increases the horizontal sight distance on curves. It reduces accident potential when vehicle stop during emergencies.
Importance of Road Shoulder
3.00 m.
Lately, the width of the road was standardized to --------- for first class paved one lane highway
◼ 1. Separation of vehicular flows. ◼ 2. Separation of conflicts. ◼ 3. Reduction in excessive pavement areas. ◼ 4. Reduction of traffic and indications of proper use of intersections. ◼ 5. Arrangement to favor a prominent turning movement. ◼ 6. Location of traffic control devices
Island is included in the design of intersections for the following purposes:
highway median
It is an effective means of reducing headlight glares, conflicts, and accident between opposing streams of traffic.
highway median
It makes turning of vehicles smooth and safe operation.
60 to 120 centimeters wide
Most of the road shoulders in rural areas are unpaved having a width of ------------- either earth filled or graveled surface that during rainy days, drivers are hesitant to occupy.
◼ 1. It requires large area of land. ◼ 2. At higher design speed, more time is consumed just to traverse the longer loops. ◼ 3. Vehicles making left turn execute 270⁰ right turn and travel greater distance becoming very unpleasant and hazardous due to the sharp curves and steep grades. ◼ 4. Vehicles leaving the curve loop in one quadrant weave those entering the adjacent loop from the through roadway.
Objections to the Cloverleaf Interchange Design
3.00 or 3.60 meters
Outside shoulder should be paved for at least ------------- wide if truck volume is more than 250 in the design hour (ADT)
low-speed urban streets
Superelevation may be omitted on ------------------ where severe constraints are present
8%
Superelevation rates above ----- are only used in areas without snow and ice
3.00 to 9.00 meters
The Policy on Geometric Design states that, ------------ median width is appropriate in suburban or mountainous situations
All inter-town or city highways shall be provided with edge line and may be used on other classes of roads.
The Uniform Traffic Control Device Manual provides that:
◼Outside shoulder should be paved for at least 3.00 or 3.60 meters wide if truck volume is more than 250 in the design hour (ADT). ◼ The recommended width of left (median) shoulder is 1.20 to 2.40 meters with at least 1.20 meters paved. ◼ If there are 6 or more lanes, the median shoulder should be 3.00 meters wide or 3.60 meters if truck volume in the design hour exceeds 250. ◼ For arterials with ADT less than 400 the usable shoulder width is fixed at 1.20 meters minimum, although 2.40 meters wide is much preferred. ◼When the design hour volume ADT exceeds 400, the usable minimum shoulder width is 2.40 meters although 3.60 meters is recommended. ◼ For Urban Arterial Road, similar shoulder without curb is suggested unless needed for proposed drainage. ◼ The width of median shoulder on four lanes divided arterials is fixed at 90 centimeters as minimum. ◼ For six or more lanes, 2.40 to 3.00 meters shoulder width is recommended. ◼ For Rural Collectors Roadway, 60 centimeters wide graded shoulder is required for ADT's less than 400 ◼ For ADT's over 2000, 2.40 meters wide shoulder is recommended.
Policy on Geometric Design Recommended that:
trends in forecast and legislation
The association also publishes the AASHTO quarterly reports on current Highway and Transportations subject including ----------------
The centerline of each individual roadway at profile grade is maintained while raising the outer edge and lowering the inner edge to attain the desired super elevation. It is done by raising-up the outside edge of the pavement with relation to the centerline until the outer half of the cross section is flat. Then, the outer edge is raised until the cross section is straight. Finally, the entire cross section is rotated as a whole until full super elevation is reached.
The centerline of each individual roadway at profile grade is maintained while raising the outer edge and lowering the inner edge to attain the desired super elevation. It is done by raising-up the outside edge of the pavement with relation to the centerline until the outer half of the cross section is flat. Then, the outer edge is raised until the cross section is straight. Finally, the entire cross section is rotated as a whole until full super elevation is reached.
The volume of traffic. ◼ Character of the traffic. ◼ Speed of the traffic. ◼ Characteristics of motor vehicles and of the driver
The cross section of a typical highway has latitude of variables to consider such as
higher
The design speed is basically -------- than the anticipated average speed.
◼ 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"
The functions of freeway interchanges are:
Non-Traversable Energy Absorbing Devices
The line chain link fence I meter high supported by steel post augmented by cables at the bottom and midpoint. these are metal guard rail.
◼ Climate conditions ◼ Terrain conditions ◼ Type of area ◼ Frequency of very slow-moving vehicles
The maximum rates of superelevation used in highways are controlled by four factors:
AASHTO
The name was expanded in 1973, when the Department of Transportation was integrated into the association renaming AASHO to AASHTO, giving the officials of these agency the power to govern its operation.
3% to 6%; 4%
The paved shoulder cross slope ranges from -------- although ------ is the most common
1.20 to 2.40 meters
The recommended width of left (median) shoulder is ---------- with at least 1.20 meters paved
diamond type
The simplest and low cost form of interchange is the ? It is recommended where the freeway crosses nonfreeway arteria
2.00 meters
The width is--------------- minimum for a 2-way travel. The grade of the lane is 570 maximum on short distances
90 centimeters
The width of median shoulder on four lanes divided arterials is fixed at -------------- as minimum.
Deterring Devices.
Two sets of double strip painted on the existing pavement, raised diagonal bars, low curbing and shallow ditches.
2.40 meters; 3.60 meters
When the design hour volume ADT exceeds 400, the usable minimum shoulder width is ------- although --------- is recommended.
18 to 27 meters
Where space and cost permit, wide median is highly recommended. For rural sections of freeway, the --------- wide median is being adopted
7.00 meters; 4.80 meters
With regards to the vertical clearance height, the railroad requires a minimum of ------- as against ------- clear distance above the highway.
true
Within an intersection, median is considered an island.
12%
a super e should not exceed at a rate of?
◼ It is an effective means of reducing headlight glares, conflicts, and accident between opposing streams of traffic. ◼ The Median offers refuge between opposing traffic stream of cross traffic, and pedestrian could traverse each stream at separate maneuvers. ◼ Median provides available space for left turn lanes. ◼ It makes turning of vehicles smooth and safe operation. ◼Where space and cost permit, wide median is highly recommended. For rural sections of freeway, the 18 to 27 meters wide median is being adopted. ◼ The Policy on Geometric Design states that, 3.00 to 9.00 meters median width is appropriate in suburban or mountainous situations. ◼ For rural and urban arterials, 18.00 meters median or wider is preferred because it allows the use of independent profiles and at the same time minimizes cross over accident.
advantages of highway median
4-6%
super e that is applicable for urban design in areas with little or no constraints
4.50 meters
the total surface width of the roadway was only --------
20 to 30 kilometers per hour
in a bicycle lane, the design speed is ------------- for flat section.
An island
is a defined area between traffic lanes for control of vehicle movement and for pedestrian refuge.
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.
Grade line
is defined as the longitudinal profile of the highway y as a measure how the centerline of the highway rises and fall
cross slope
is provided in all tangent sections of the roadway.
AASHTO
is the American Association of State Highway and Transportation Officials
Consistency
is the most important single rule in highway design. That is, by making every element of the roadway conforms to the expectation of every driver.
The AASHTO practice
is to classify first the highway as Rural or Urban, then as Freeways, Arterials, Collectors and Local
3.60 meters; 3.60 to 4.20 meters
now ------- wide surface was adopted standard for freeways and other major traffic roadways, although there are strong demand to increase it further from ---------
The Median
offers refuge between opposing traffic stream of cross traffic, and pedestrian could traverse each stream at separate maneuvers
Median
provides available space for left turn lanes
1:1
ratio of Slope of cuts through an ordinary undisturbed earth fill
1:2 and sometimes 1:4 proven to be stable.
ratio of rock cuts could be as steep as ------------
plants
reduced erosion and decreases maintenance costs.
Frontage road
shall be permitted to enter connecting cross streets only at a distance of at least 100 meters for rural road and 50 meters for urban conditions.
reducing the super elevation combined with easement curves, delineators, striping signs and rumble strips
some motorists drive faster on straight road alignment or less sharply curved sections Under this situations, highway design adopted control by?