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Methodology VMBI

The Vehicle Mounted Bump Integrator is used to measure road unevenness by recording the displacement of a vehicle's chassis relative to its rear axle. It contains an integrating unit fitted to the rear axle that converts the differential movement between the axle and vehicle body into electrical pulses recorded by counters. Maintaining consistent vehicle speed is important for accurate measurements. Software then evaluates total bump counts, distance traveled, and speed. IRC SP 16:2004 provides roughness classification standards in mm/km for bituminous and cement concrete roads ranging from good to poor condition based on measured values.

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119 views1 page

Methodology VMBI

The Vehicle Mounted Bump Integrator is used to measure road unevenness by recording the displacement of a vehicle's chassis relative to its rear axle. It contains an integrating unit fitted to the rear axle that converts the differential movement between the axle and vehicle body into electrical pulses recorded by counters. Maintaining consistent vehicle speed is important for accurate measurements. Software then evaluates total bump counts, distance traveled, and speed. IRC SP 16:2004 provides roughness classification standards in mm/km for bituminous and cement concrete roads ranging from good to poor condition based on measured values.

Uploaded by

Mohan Mylarappa
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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1.

INTRODUCTION

The Vehicle Mounted Bump Integrator (VMBI) is a component of the road


measurement data acquisition system. It is a response-type road unevenness meter, which is
mounted in a vehicle to monitor pavement unevenness. It records the displacement of the
vehicle chassis relative to the rear axle per unit distance travelled, usually in terms of
counts/km or m/km.
2. UNEVENNESS MEASUREMENT USING VMBI

VMBI consists of an integrating unit; the integrating unit is fitted with the rear axle and
mounted in the rear portion of the car or rear floor of a jeep. The differential movement between
the rear axle and the body of the vehicle due to road unevenness is measured by the upward
vertical motion of a wire which is transmitted into unidirectional rotatory movement of the pulley
of the integrator unit. There is an arrangement in the integrating unit for converting the rotational
movement into electric pulses which is recorded by the counters.
The road roughness is affected by the vehicle speed. A bump gets magnified if the
vehicle speed is not maintained. For getting the realistic values the vehicle speed must be
maintained with in the calibrated speed. It has ensured that the outer vehicle wheel travels on
the wheel path.
With the help of the software, the total number of bump counts made, the distance
covered and the speed of travel is evaluated. The data obtained is saved for further
calculations.
3. ROUGHNESS CLASSIFICATION BASED ON IRC SP 16:2004

As per the IRC Code SP 16:2004, Table 3, the recommended standard for roughness values
and the maximum permissible values of roughness (mm/km) for road surface is as follows:

Condition of Road Surface


Sl No Type of Surface
Good Average Poor
1. Bituminous Concrete < 2000 2000-3000 >3000
2. Cement Concrete < 2200 2200-3000 >3000

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