Highway and Specialized Testing

Axle Load Test Services for Highways

Vehicle axle load measurement and spectrum analysis for pavement design

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IRC SP 72:2015 IRC 37:2018 Motor Vehicles Act 1988
An axle load survey measures the actual wheel and axle loads of commercial vehicles using portable weigh pads deployed on the highway. The resulting axle load spectrum is the critical input for computing the Vehicle Damage Factor (VDF) and converting mixed traffic into Equivalent Standard Axle Loads (ESALs) for pavement design.

What Is an Axle Load Survey?

The axle load test involves weighing individual axles of commercial vehicles — trucks, trailers, buses, and multi-axle vehicles — as they pass over portable electronic weigh pads placed on the road surface. Each vehicle is classified by its axle configuration (single, tandem, or tridem), and the load on each axle group is recorded. The collected data builds an axle load frequency distribution (axle load spectrum) for each vehicle category. This axle load spectrum is used to compute the Vehicle Damage Factor (VDF) using the fourth-power law, where pavement damage increases exponentially with axle load. The VDF converts actual heterogeneous traffic into equivalent standard axle repetitions, which is the traffic input for IRC 37 flexible pavement design. An overloaded truck with 14 tonnes on a single axle causes over 4.5 times more damage than the legal limit of 10.2 tonnes — making accurate axle load data essential for realistic pavement design. NKMPV conducts axle load surveys in conjunction with ATCC traffic volume surveys to provide a complete traffic characterisation package. Our surveys cover national highways, state highways, and expressways across Haryana, Punjab, Himachal Pradesh, and Rajasthan. The data also supports overloading assessment studies and enforcement planning for transport authorities. Combined with CBR test results, the axle load data enables complete pavement crust design per IRC 37.

Test Parameters & Acceptance Criteria

The following parameters are recorded and computed from the axle load survey. Legal axle load limits per Motor Vehicles Act and MoRTH specifications are used as acceptance benchmarks.

Parameter Value / Range Unit Standard
Single Axle Load (Legal Limit) 10.2 tonnes (100 kN) tonnes Motor Vehicles Act / IRC 37
Tandem Axle Load (Legal Limit) 19.0 tonnes (186 kN) tonnes Motor Vehicles Act / IRC 37
Tridem Axle Load (Legal Limit) 24.0 tonnes (235 kN) tonnes Motor Vehicles Act / IRC 37
Gross Vehicle Weight (2-axle truck) 16.2 tonnes (legal maximum) tonnes CMVR Rule 93
Vehicle Damage Factor (VDF) 1.5-5.5 (typical range) dimensionless IRC 37 Cl. 5.2
Standard Axle Load 80 kN (8.16 tonnes) kN IRC 37 Cl. 2.1
Minimum Sample Size >= 300 commercial vehicles per direction vehicles IRC SP 72 Annexure-A
Overloading Percentage Typically 40-70% vehicles exceed legal limits % Survey observation
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Applicable Indian Standards

IRC SP 72:2015

Guidelines for the Design of Flexible Pavements for Low Volume Rural Roads (Annexure-A: Axle Load Survey Methodology)

IRC 37:2018

Guidelines for the Design of Flexible Pavements

Motor Vehicles Act 1988

Central Motor Vehicle Rules — Rule 93 (Maximum Permissible Axle Loads and GVW)

MoRTH 5th Revision

Specifications for Road and Bridge Works — Section 900 (Traffic and Transportation)

IRC 58:2015

Guidelines for the Design of Plain Jointed Rigid Pavements for Highways

Equipment Used

Portable Electronic Weigh Pads

Low-profile axle weighing pads (pair)

20 tonnes per pad, resolution 10 kg, suitable for single/tandem/tridem axle configurations

Calibrated

Weigh Pad Digital Indicator

Handheld wireless display unit

Displays individual axle loads, tandem/tridem group loads, and gross vehicle weight simultaneously

Calibrated

Portable Steel Ramps

Approach and departure ramps (pair per pad)

Gradual incline to pad surface, prevents impact loading and ensures accurate static weighment

Calibrated

Data Recording Laptop and Software

Field laptop with custom axle load data entry software

Records vehicle type, axle configuration, individual axle loads, GVW, registration number, and commodity type

Calibrated

Traffic Control Equipment

Cones, sign boards, and safety jackets

Traffic diversion and safety setup for vehicle stopping and weighing operations on live carriageway

Calibrated

Survey Process

1

Site Selection & Coordination

Day 1

A suitable weighing location is identified on the project highway — typically a straight, level section with sufficient shoulder width for vehicles to queue and be diverted for weighing. Coordination with local traffic police and highway authorities is arranged for traffic control during the survey. The site must be away from toll plazas and weigh bridges to avoid biased samples of vehicles that have already adjusted their loads.

2

Equipment Setup & Calibration

Day 1

Portable weigh pads are placed on a level pavement surface with approach ramps. The system is calibrated using known calibration weights and cross-verified by weighing a reference vehicle with known axle loads. Traffic control measures including cones, sign boards, and flagmen are deployed. The team is briefed on vehicle classification, axle configuration identification, and data recording protocols.

3

Vehicle Interception & Weighing

Days 2-4 (3 days typical)

Commercial vehicles (trucks, trailers, buses, multi-axle vehicles) are randomly intercepted from the traffic stream — targeting a minimum of 300 commercial vehicles per direction as per IRC SP 72. Each vehicle is directed over the weigh pads one axle at a time. The load on each individual axle is recorded, along with the vehicle type, axle configuration (single, tandem, tridem), number of tyres, registration number, and commodity carried.

4

Data Compilation & Validation

Day 5

Field data is entered into spreadsheets and validated for consistency. Gross Vehicle Weight is cross-checked against the sum of individual axle loads. Outliers and erroneous readings are flagged and verified against field notes. Vehicles are grouped by IRC classification categories: two-axle rigid trucks, three-axle rigid trucks, four-axle semi-trailers, five-axle articulated vehicles, multi-axle vehicles, and buses.

5

Axle Load Spectrum Development

Day 5-6

Axle loads are tabulated into frequency distribution tables (axle load spectrum) separately for single axles, tandem axles, and tridem axles within each vehicle class. The spectrum shows the percentage of axles falling in each 1-tonne or 2-tonne load interval. Overloading percentage is computed as the proportion of axles exceeding legal limits.

6

VDF Calculation & ESAL Computation

Day 6

The Vehicle Damage Factor (VDF) is calculated for each vehicle class using the fourth-power law: VDF = summation of (individual axle load / standard 80 kN axle load)^4 across all axles. The weighted average VDF across the fleet is then multiplied by the AADT of commercial vehicles from the traffic survey to compute total Equivalent Standard Axle Load repetitions over the design life in million standard axles (MSA).

7

Report Preparation & Delivery

Days 7-8

The final axle load survey report includes individual vehicle data sheets, axle load frequency distributions, axle load spectra charts, VDF calculations by vehicle class and overall fleet, overloading analysis, and design traffic computation in MSA. Reports are formatted per NHAI DPR requirements and IRC SP 72 guidelines. Digital and hard copies are delivered to the client.

Where Axle Load Surveys Are Used

Axle load survey data is indispensable for accurate pavement design. Under IRC 37 guidelines, the VDF derived from axle load surveys converts actual traffic into equivalent standard axle loads — the fundamental design input. Using default VDF values from IRC 37 Table 2 instead of site-specific data can lead to under-designed or over-designed pavements, both resulting in significant cost implications. For overlay design of existing roads, axle load data combined with ATCC traffic volume data provides the loading history needed for remaining life analysis. Transport departments also use axle load survey data to assess the extent of overloading on highway corridors and plan enforcement strategies.
VDF computation for flexible pavement design per IRC 37 ESAL calculation for rigid pavement design per IRC 58 DPR preparation for national and state highway projects Overloading assessment and enforcement planning for transport authorities Overlay and strengthening design for existing pavements Bridge loading assessment and load rating studies Toll revenue estimation based on vehicle weight categories Comparison of actual vs. legal axle load compliance

Detailed Information

Axle Load Testing is a critical field investigation used to measure the actual axle-wise load carried by commercial vehicles operating on highways. These measurements are essential for pavement design, pavement performance evaluation, traffic studies, and compliance with IRC and MoRTH specifications. NKMPV Lab provides professional axle load test services for highways to support NHAI projects, expressways, state highways, and urban road infrastructure.

Our axle load surveys help engineers understand real traffic loading conditions, which directly influence pavement thickness design, remaining life assessment, and maintenance planning.

What is an Axle Load Test?

An axle load test is the process of measuring the load carried by individual axles of vehicles passing over a roadway. Each axle load contributes differently to pavement stress, fatigue, and long-term deterioration. Unlike gross vehicle weight alone, axle-wise load distribution provides accurate input for pavement engineering analysis.

Axle load data is collected using calibrated weighing systems installed temporarily or permanently on the roadway, ensuring precise and repeatable measurements under live traffic conditions.

Importance of Axle Load Testing in Highway Projects

Axle load testing plays a vital role in highway planning, design, and asset management. Real-world traffic loading often differs from assumed design values, making field-based axle load measurement essential.

Key benefits include:

  • Accurate input for pavement thickness design

  • Assessment of overloading trends on highways

  • Evaluation of pavement deterioration and fatigue life

  • Support for traffic and transport studies

  • Compliance with IRC and MoRTH guidelines

Without axle load data, pavement designs may be either overdesigned (increasing cost) or underdesigned (leading to premature failure).

Applications of Axle Load Test Services

Axle load testing is widely used across various highway and infrastructure projects, including:

  • National Highway Authority of India (NHAI) projects

  • Expressways and access-controlled highways

  • State highways and major district roads

  • Pavement rehabilitation and strengthening projects

  • Traffic impact assessment studies

  • Overloading enforcement and policy studies

The test results are often combined with traffic volume data to calculate cumulative traffic loading in terms of standard axles.

Axle Load Testing Methodology

The axle load test is carried out using calibrated load measurement equipment placed on the carriageway. Vehicles are guided to pass over the weighing system at controlled speeds to ensure accurate readings.

The test records:

  • Individual axle loads

  • Axle configuration

  • Vehicle class

  • Gross vehicle weight

  • Load distribution patterns

Multiple vehicle passes are recorded to develop a statistically reliable axle load spectrum for the project corridor.

Standards and Specifications Followed

Axle load testing services are conducted in accordance with applicable Indian road standards and guidelines, including:

  • IRC guidelines for traffic loading and pavement design

  • MoRTH specifications for highway works

  • Relevant provisions used in NHAI projects

All testing procedures and reporting formats are aligned with standard engineering practices accepted by government authorities and consultants in India.

Role of Axle Load Data in Pavement Design

Axle load data is a key input for both flexible and rigid pavement design. The measured axle load spectrum is used to calculate cumulative standard axle repetitions, which directly influence pavement thickness and material selection.

Accurate axle load data helps:

  • Predict pavement fatigue and rutting

  • Estimate remaining pavement life

  • Design overlays and strengthening measures

  • Improve long-term pavement performance

Integration with Other Highway Surveys

Axle load testing is often conducted alongside other highway evaluation studies such as traffic surveys, pavement condition surveys, and network-level assessments. When combined with these studies, axle load data provides a comprehensive understanding of road performance under actual traffic conditions.

Advantages of Professional Axle Load Testing

Using professional axle load test services ensures:

  • Reliable and repeatable measurements

  • Compliance with project specifications

  • Accurate traffic loading inputs

  • Reduced risk of pavement design errors

  • Better decision-making for maintenance planning

Field data collected under real traffic conditions is far more dependable than assumed or theoretical loading values.

Why Choose NKMPV Lab for Axle Load Testing?

NKMPV Lab provides axle load test services with a focus on accuracy, compliance, and engineering reliability. Our testing approach supports consultants, contractors, and government agencies involved in highway and infrastructure development.

We deliver clear, structured test reports suitable for use in:

  • DPR preparation

  • Pavement design calculations

  • NHAI and state highway submissions

  • Technical audits and reviews

Conclusion

Axle Load Test Services for Highways are essential for understanding real traffic loading and ensuring safe, durable, and cost-effective pavement designs. Accurate axle load measurement helps engineers assess overloading impacts, predict pavement life, and design highways that perform reliably under actual operating conditions.

By conducting axle load testing as per IRC and MoRTH practices, highway authorities and project stakeholders can make informed decisions that improve road safety, optimize construction costs, and extend pavement service life.

Why Choose NKMPV for Axle Load Surveys?

NABL Accredited Survey Reports

Our axle load survey reports carry NABL accreditation (ISO/IEC 17025:2017), accepted by NHAI, state PWDs, highway consultants, and arbitration tribunals without additional verification.

Calibrated Portable Weigh Pads

Our electronic weigh pads are calibrated with NABL-traceable standards and cross-verified before each survey deployment. The 10 kg resolution ensures accurate axle load readings even for lightly loaded vehicles.

Combined Traffic and Axle Load Packages

We deploy ATCC traffic counters and axle load survey teams simultaneously, providing both traffic volume and axle load spectrum data from a single mobilisation — saving time and cost for DPR-level highway projects.

Statistically Valid Sample Sizes

We ensure a minimum of 300 commercial vehicles per direction are weighed, covering all vehicle classes proportional to their traffic share. This exceeds the minimum requirements of IRC SP 72 and ensures statistically reliable VDF values.

Experienced Field Survey Teams

Our teams have conducted axle load surveys on major highway corridors including NH-44, NH-5, NH-7, and NH-152 across Haryana, Punjab, Himachal Pradesh, Uttarakhand, and Rajasthan, handling diverse traffic compositions from heavily overloaded mining trucks to multi-axle container carriers.

Frequently Asked Questions

The legal single axle load limit for trucks in India is 10.2 tonnes (100 kN) as per the Central Motor Vehicle Rules (CMVR) Rule 93. Tandem axle groups are limited to 19.0 tonnes, and tridem axle groups to 24.0 tonnes. The standard axle load used for pavement design per IRC 37 is 80 kN (8.16 tonnes), representing a single axle with dual tyres.
VDF is calculated using the fourth-power law. For each axle of a vehicle, the equivalence factor = (actual axle load / 80 kN)^4. The VDF for that vehicle is the sum of equivalence factors across all its axles. For example, a two-axle truck with front axle at 4 tonnes and rear axle at 14 tonnes has VDF = (4/8.16)^4 + (14/8.16)^4 = 0.058 + 8.67 = 8.73. The fleet-average VDF is the weighted mean across all weighed vehicles.
IRC SP 72 recommends a minimum of 300 commercial vehicles per direction for a statistically valid axle load survey. The sample should be representative of the actual traffic composition, covering all vehicle classes — two-axle trucks, three-axle trucks, multi-axle vehicles, trailers, and buses. NKMPV typically weighs 400-600 vehicles per direction to ensure robust VDF estimates.
IRC 37 Table 2 provides default VDF values (e.g., 2.5 for initial traffic and 4.5 for terminal traffic on NH/SH) that are national averages. Actual VDF on a specific corridor can vary significantly — from 1.5 in regions with light commercial traffic to 6.0+ on mining or industrial corridors with severe overloading. Using default values can lead to under-designed or over-designed pavements, resulting in premature failure or unnecessary cost.
An axle load survey measures loads on random vehicles in the actual traffic stream, capturing the real loading pattern including overloaded vehicles. Weighbridge data at toll plazas or check posts typically records only Gross Vehicle Weight and may not capture axle-level data. Additionally, vehicles at weighbridges may have adjusted their loads to comply with limits. For pavement design, random roadside axle load survey data per IRC SP 72 is the accepted method.
Yes, NKMPV routinely conducts combined ATCC traffic volume surveys and axle load surveys as a single mobilisation package. The ATCC provides classified traffic volume data (ADT, AADT), while the axle load survey provides the VDF. Together, these two datasets provide all traffic inputs needed for complete pavement design per IRC 37 and IRC 58.

Related Testing Services

Traffic Survey Services (ATCC)

Classified traffic volume count and axle load data collection per IRC SP 72/106.

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Flexible Pavement Design

Pavement crust thickness design using CBR and traffic data per IRC 37:2018.

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California Bearing Ratio (CBR) Test

Subgrade strength evaluation for road and pavement design per IS 2720 Part 16.

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Roughness Test by Fifth Wheel Bump Integrator

Pavement riding quality measurement using bump integrator per IRC SP 16.

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