--- title: "Preliminary survey method" subject: "Transportation Engineering I" chapter: 2 key: "semester_6/transportation_engineering_i:preliminary-survey" source: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/preliminary-survey site: BCT Engineering --- # Preliminary survey method Transportation Engineering I · Chapter 2: Highway Alignment and Engineering Survey - Asked in: 2080 Chaitra, 5 marks; 2077 Chaitra, 4 marks; 2072 Ashwin (asked 3 times) - Video: [Survey for Road Project (Reconnaissance, Preliminary Survey etc) | Highway Engineering L-03| dAd Sir](https://www.youtube.com/watch?v=4Kbf6GF0hOc) — dAd Sir - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/preliminary-survey - Whole chapter: https://www.bctengineer.com/md/semester_6/transportation_engineering_i/chapter-2 ## Question Describe the procedure (conventional method) of carrying out preliminary survey for a proposed highway alignment. ## Short answer Conventionally, a traverse is run along each route, levelling and cross-sectioning are performed, and a 100–200 m wide strip is contoured. Drainage, soil, material, and traffic data are gathered, and cost estimates compare alternatives to select the final alignment. ## Answer The preliminary survey is a detailed instrumental survey of the routes chosen after the reconnaissance, carried out to compare them and fix the best alignment. Its objectives are to collect topographic and other data, estimate the cost and select the final alignment. #### Conventional method - procedure 1. **Primary traverse:** a closed or open traverse is run along each route using a theodolite or total station, with chainage pegs at 20-30 m (or 50 m) intervals; the traverse stations are tied to the main control points. 2. **Levelling:** longitudinal levelling along the traverse, and cross-sections at regular intervals (about 50-100 m in plains, 20-30 m in hills) extending across the survey strip on each side; bench marks established at about every 250-500 m. 3. **Topographic detail:** details such as streams, buildings, roads, fields and trees are surveyed in a strip about 100-200 m wide (contour interval 1-2 m) to prepare the contour plan. 4. **Drainage and hydrology data:** stream crossings, catchments, high flood level, existing structures. 5. **Soil and geology survey:** soil classification and CBR/subgrade tests at intervals; location of quarries and construction materials. 6. **Traffic and land use data** where needed. 7. **Cost estimate** of each alternative route, including earthwork, pavement, cross-drainage works and land. 8. **Comparison** of the alternatives and selection of the final route. #### Result The contour plan, longitudinal section and estimates are prepared; the chosen alignment is then marked in the field for the final location survey. Modern practice uses total stations, GPS, drone/aerial photogrammetry and digital terrain model software (the *aerial method*), which saves time. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. How is the primary traverse run in the conventional preliminary survey? A. Using only a compass without pegs B. With a theodolite or total station along each route, with chainage pegs at regular intervals C. By aerial photograph only D. With a pocket altimeter Answer: B. A traverse is run along each route with a theodolite/total station and pegged at 20-30 m (or 50 m) chainage. (Key point: Primary traverse) 2. What levelling is done during the preliminary survey? A. Only the centre line is levelled B. No levelling is needed C. Levelling is done only at bridges D. Longitudinal levelling with cross-sections and bench marks about every 500 m Answer: D. Longitudinal levels and cross-sections are taken, with bench marks established at about 500 m. (Key point: Levelling) 3. What is the strip plotted to prepare the contour plan? A. About 100-200 m wide, with 1-2 m contour interval B. About 5 km wide C. About 5 m wide D. Exactly the carriageway width Answer: A. Details are plotted in a 100-200 m strip with contours at 1-2 m interval. (Key point: Topographic strip) 4. How is the final route selected in the preliminary survey? A. By the shortest length only B. By estimating cost of each alternative and comparing them C. By choosing the first route surveyed D. By the engineer's guess Answer: B. Cost estimates of each alternative, including earthwork, pavement, drainage and land, are compared to select the final route. (Key point: Final steps) ## Related in Transportation Engineering I - [Stages of engineering survey for alignment](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Asurvey-stages) — Transportation Engineering I, chapter 2, asked 7× - [Requirements of ideal highway alignment](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Aalignment-requirements) — Transportation Engineering I, chapter 2, asked 12× - [Factors controlling highway alignment](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Aalignment-factors) — Transportation Engineering I, chapter 2, asked 12× - [Definition of highway alignment](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Adefine-alignment) — Transportation Engineering I, chapter 2, asked 4× - [Final location and detailed survey](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Adetailed-survey) — Transportation Engineering I, chapter 2, asked 3× - [Updating information across survey stages](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Ainfo-updated-stages) — Transportation Engineering I, chapter 2, asked 3× ## Related in other subjects - [Tunnel alignment survey and ideal bridge location](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Atunnel-alignment-survey-ideal-bridge-location) — Transportation Engineering II, chapter 5 - [Procedure of preliminary estimate (office building)](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Aprelim-estimate-procedure-office) — Estimating and Costing, chapter 3, asked 2× - [Case study: workflow, factors, proposed design, benefits](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Acs-2076chaitra) — Instrumentation II, chapter 10 - [Conventional tunnelling steps and TBM advantage](https://www.bctengineer.com/question.md?key=semester_8%2Fconstruction_management%3Atunnelling-conventional-tbm) — Construction Management, chapter 4