Highway Route Location Survey Notes
Highway Route Location Survey: Principles and Objectives
Course Information: This lecture is part of CIVL 314 Highway Engineering, delivered by Ing. Dr. E. K. Nyantakyi, F-GHIE, Senior Lecturer, on June 5, 2026.
Definition: Route location survey draws on engineering principles, planning, geology, economics, and surveying.
Primary Aim: The major goal is to select a roadway alignment that best satisfies traffic desires and transportation needs within a region, district, locality, or travel corridor. This must be achieved at a minimum overall cost to the economy and with the least destruction to the environment.
Key Consideration Factors: - Topography and the nature of the terrain. - Drainage characteristics. - Availability of construction materials. - Land use patterns. - Social, political, and economic considerations.
General Guidelines for Route Location Survey
Challenge of Scale: Selecting a route through a vast terrain for a facility that only covers a small strip of land in lateral extent can be intimidating. Guidelines help reduce the "solution space" to find the best options efficiently.
Directness of Route: The shortest path between two points is a straight line. Where possible, the route must be as direct as possible.
Traffic Operations Needs: The location should meet major traffic desire lines and allow for continuous, free-flowing, and convenient traffic operations.
Topographical Considerations: In hilly terrain, routes should cross ridges at their lowest points to ensure manageable gradients, cheaper construction, and more economical vehicle operating costs.
Earthworks: Areas requiring deep cuttings, expensive tunneling, or extensive earthworks should be avoided to manage costs.
Availability of Construction Materials: Routes should be located near material sources to avoid high costs associated with hauling materials over long distances.
Drainage Considerations: Areas prone to frequent flooding, such as valleys and low-lying areas, must be avoided. This includes marshy or swampy locations or spots requiring many expensive cross-drainage structures.
Suitable Bridge Sites: Route selection should minimize the need for long, expensive bridges. Bridge locations at river bends must be avoided because they are prone to foundation scouring at the piers.
Balance of Cuttings and Fills: The route should aim for a balance between cut and fill material to minimize the need for hauling material to or from the site.
Passage Through Urban Areas: When passing through urban settings, the route should utilize undeveloped or "blighted" areas (slums and low-cost areas) to minimize property compensation claims.
Land Use Patterns: Routes should avoid large-scale farms, settlements, and industrial facilities. If passing through settlements, the road should be placed on the outskirts/periphery to prevent through traffic from becoming a nuisance.
Accessibility: In rural areas, the route must provide access to farming settlements, market centers, and rural communities, often by connecting to existing roads.
Geologic Considerations: Locations with significant rock outcrops or surface rock requiring blasting and excavation should be avoided due to the high cost.
Historic, Social, and Cultural Sites: Locations with cultural value (e.g., cemeteries, schools, hospitals, places of worship, recreational grounds) must be preserved and avoided by the selected route.
Stages of Route Survey Selection
Selection is broken into four distinct stages to find the final and best route:
Map Study.
Reconnaissance Survey.
Preliminary Survey.
Final Location and Detailed Survey.
Stage 1: Map Study
Definition: A desk study involving a topographical map of the area conducted in the office before any site visit.
Purpose: To provide likely possible routes and eliminate unfeasible ones.
Ghana Specifics: Topographical maps represent contour intervals at or . These maps are available at the Ghana Survey Department.
Utility: Features such as lakes, swamps, ponds, hills, and major rivers provide clues that reduce the band of the region within which feasible alignments may lie.
Stage 2: Reconnaissance Survey
Definition: An evaluation of the feasibility of one or more possible routes between specific points that may be several kilometers apart.
Process: Involves studying existing maps/aerial photographs and field inspection by a team along a long stretch of proposed alternative routes.
Data Collection Details: - Identification of valleys, ridges, marshy lands, and permanent structures not on the map. - Establishing gradients, lengths of gradients, and possible curve radii. - Determining the number and type of cross-drainage structures. - Observing maximum flood levels and natural groundwater levels. - Identifying sources of construction materials, water, and potential stone quarry sites. - Hilly/Mountainous Terrain specifics: Observations of rock types, dip of strata, seepage flows, and identifying stable vs. unstable sides of the hill.
Stage 3: Preliminary Survey
Definition: A large-scale study of one or more feasible routes to finalize the best alignment and estimate costs.
Objectives: - Survey alternative alignment proposals from the reconnaissance phase. - Compare different proposals. - Estimate quantities of earthworks and construction costs.
Ground Survey Method: - Used when alternative alignments fall within a narrow right-of-way. - Involves a line traverse using a theodolite for angle measurements. - Levels are taken at mapped stations, breaks in the ground, cross-roads, and streams. - Cross-sections are established at specific intervals. - A final strip map of the right-of-way with contours is produced.
Aerial Survey Method: - Suited for vast areas or rugged terrain where reconnaissance could not approximate the final alignment closely. - Steps: Taking aerial photographs with longitudinal/lateral overlaps, examining photos under stereoscopes, and selecting control points. - Uses photo interpretation for geological features, soil conditions, and drainage requirements.
Stage 4: Final Location and Detailed Survey
Purpose: To establish the centerline in the field and collect physical data for construction plans.
Fieldwork Details: - The centerline is established following the preliminary survey line as closely as possible, using a theodolite and steel tapes. - Temporary benchmarks are fixed at intervals of approximately . - Profile levels are taken along the centerline at each station and at points with significant slope changes. - Leveling extends beyond the beginning and end points to allow for merging with other roads. - Cross-section levels are taken up to the desired road width at intervals of (or closer if terrain changes abruptly). - Detailed surveys of all river crossings, streams, and ditches are conducted for considerable distances on either side.
Detailed Property and Structure Information: - Recording property corners, fences, and man-made developments. - Cataloging existing culverts and bridges (type, size, quantity, number of openings, elevations, stream bed details, and flood levels).
Soil Survey: - Elaborate soil sampling is performed to draw a soil profile. - Sampling depths typically range from below ground level. - Spacing of borings depends on soil types.
Questions and Assignment I
Assignment Tasks: - Define the major aim of a route location survey. - Explain the following five guidelines: Directness of routes, Traffic operations needs, Topographical considerations, Earthworks, and Availability of construction materials. - State any five factors to be taken into consideration during a route location survey. - State and explain the four main stages in a route location survey.