---
title: "Requirements of ideal highway alignment"
subject: "Transportation Engineering I"
chapter: 2
key: "semester_6/transportation_engineering_i:alignment-requirements"
source: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/alignment-requirements
site: BCT Engineering
---

# Requirements of ideal highway alignment

Transportation Engineering I · Chapter 2: Highway Alignment and Engineering Survey

- Asked in: 2080 Chaitra, 3 marks; 2079 Jestha, 4 marks; 2078 Chaitra, 2 marks; 2077 Chaitra, 4 marks; 2076 Bhadra; 2075 Bhadra; 2075 Baisakh; 2073 Bhadra; 2072 Magh; 2070 Bhadra; 2069 Bhadra; 2068 Bhadra (old course), 4 marks (asked 12 times)
- Video: [Requirements Of  #HighwayAlignment| Ideal Alignment|Best Route Location|Transportation Engineering](https://www.youtube.com/watch?v=m3kT1U0OfWA) — DIPAK  MANDAL
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/alignment-requirements
- Whole chapter: https://www.bctengineer.com/md/semester_6/transportation_engineering_i/chapter-2

## Question

What are the requirements of an ideal highway alignment?

## Short answer

An ideal highway alignment is short, easy (gentle grades and curves), safe (adequate sight distance), and economical (low construction and operating costs). It serves traffic generators, uses stable ground, minimizes crossings and land acquisition, and allows future widening.

## Answer

The **alignment** of a highway is the position of its centre line on the ground. An ideal alignment should be **short, easy, safe and economical** (the four basic requirements).

#### Requirements
1. **Short:** a straight line is the shortest route; a short alignment saves construction and vehicle operating cost.
2. **Easy:** gentle gradients and flat curves, so that vehicles can run smoothly at the design speed. The gradient should not exceed the ruling gradient.
3. **Safe:** adequate sight distance; no sharp curves, steep grades or unstable slopes; safe at intersections and bridges; geometric design standards (NRS 2070) followed.
4. **Economical:** low initial cost (earthwork, structures) as well as low maintenance and vehicle operating cost; cut and fill balanced.
5. **Serves the needs:** passes through or near the important towns and traffic-generating points.
6. **Stable ground:** avoids landslide-prone, flood-prone, marshy and poor-soil areas.
7. **Minimum cross-drainage works:** crosses streams at right angles and at narrow, stable points, with fewer bridges and culverts.
8. **Construction materials:** available near the alignment.
9. **Minimum land acquisition,** avoiding religious and historical sites and forests as far as possible.
10. **Future expansion:** allows widening and upgrading.
11. **Hill roads:** follow the contours, use hairpin bends where necessary, and avoid steep, wet north-facing slopes.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Which are the four requirements of an ideal alignment?
   A. Short, easy, safe, economical
   B. Wide, straight, flat, cheap
   C. Fast, long, steep, safe
   D. Short, curved, steep, cheap
   Answer: A. An ideal alignment is short, easy, safe and economical. (Key point: Four requirements)

2. What does 'easy' alignment mean?
   A. Steepest gradients
   B. Gentle gradients and flat curves, with gradient not exceeding the ruling gradient
   C. Sharp curves for slow speed
   D. No drainage
   Answer: B. Easy means gentle gradients and flat curves so vehicles move smoothly at design speed. (Key point: Easy alignment)

3. How should an alignment cross streams?
   A. At acute angles at wide places
   B. At wide unstable points
   C. At right angles and at narrow, stable points
   D. Repeatedly to follow the river
   Answer: C. Right-angle crossings at narrow, stable points need fewer and smaller cross-drainage works. (Key point: Stream crossing)

4. What does economical alignment include?
   A. Only low initial cost
   B. Low initial cost plus low maintenance and vehicle operation cost, with balanced cut and fill
   C. Only shortest length
   D. Maximum earthwork
   Answer: B. It considers construction, maintenance and operating cost and balances cut and fill. (Key point: Economy)

## Related in Transportation Engineering I

- [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×
- [Requirements of highway drainage](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Arequirements-highway-drainage) — Transportation Engineering I, chapter 4, asked 6×
- [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×
- [Region, band, corridor, alignment in map study](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Amap-study-terms) — Transportation Engineering I, chapter 2

## 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
- [Requirements of an ideal boiler](https://www.bctengineer.com/question.md?key=semester_3%2Fapplied_thermodynamics%3Aideal-boiler-requirements) — Applied Thermodynamics, chapter 1