a process in Highway Engineering where the
most appropriate location, alignment, and shape of a highway are
selected.
Highway design
Five Major factors in Highway Design
*Human Factors and Driver Performance
* Vehicles
* Traffic Characteristics
* Physical Elements
* Economic Factors
Some of the most common data needed for highway design are as follows:
- Field Survey Information (Topo)
- Alignment
- Spatial Data
- AADT (Annual Average Daily Traffic)
- Subsurface Investigations
- Catchment Areas (For Cross Drain Design)
- Existing Streams/Rivers
- Existing Structures and Utility Services
a 3D representation of the project site
Topographic Surveys
It is the route of the road, defined as a series of horizontal tangents and curves. it also called the horizontal control.
Alignment
helps in better decision making when designing highways. GIS software is commonly used for identifying spatial data. QGIS is an example of a GIS software
Spatial data
the total volume of vehicle traffic on a highway or road for a year divided by 365 days.
Annual average daily traffic (AADT)
area of land that collects water after rainfall.
Water flows down into these areas and collects into rivers and streams.
Catchment Area
Design Preocedure
- Obtain topographic survey through any of the different methods
- Plot the data in any road analysis software (Civil 3D, MX Road,
OpenRoads) to model the surface - Plot the alignment
- Adjust the alignment making sure all factors are put into
consideration - Generate the existing profile
- Create a design profile making sure that it passes all design criteria
and standards - Create the cross section depending on the necessary features of
the highway - Generate the corridor
- Layout the drainage system
10.If using a pipe network for storm drains, do Rainfall Analysis and
Runoff Analysis in Storm and Sanitary Analysis (SSA)
11.If using retaining walls and structures, use slope stability software
like GEO5 for analysis
12.Add traffic signs and markings as needed
13.Iterate until optimum design is achieved
The most efficient alignment is a __________?
Straight Line
It is the target speed at which drivers are intended to travel
on a street, and not, as often misused, the maximum operating speed
Design speed
the distance at which a driver of a vehicle can see an
object of specified height on the road ahead
Sight Distance
the minimum distance required for a
vehicle, travelling at the design speed, to stop before reaching an
object in its path
Stopping Sight Distance
the distance needed for a driver to
detect an unexpected threat, recognize the threat, decide on what to do and initiate a maneuver to avoid the said threat
Decision Sight Distance
the minimum distance required to safely
make a normal passing maneuver on 2-lane highways
Passing Sight Distance
