Acceleration measurement instruments
Version : 11.0
Detailed table of contents
This chapter contains the following topics:
Summary
AMI technology
• The technology
• Approved models
• Servicing
Training
• Approved training course
• Training in the use of AMIs
Duties and responsibilities
Pre-deployment check procedures
Deployment procedures
• Before you start
• Minimise disruption
• Evidence integrity
• Conducting tests
• Data accuracy tests
After deployment procedures
• After the deployment
• Integrity of evidence
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The controlled document can be found in the Police Instructions site which is accessible via the New Zealand Police Intranet.
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Summary
Introduction
The term “Acceleration Measurement Instrument” (AMI) relates to specialist
computerised data collection equipment and its related software used to test positive or
negative acceleration of vehicles across various surface types.
AMIs are used by Police for crime scene investigation purposes, particularly to obtain
acceleration factors of motor vehicles as part of traffic crash or braking investigations.
This chapter governs the operation of AMIs.
This is an uncontrolled document printed for reference only.
The controlled document can be found in the Police Instructions site which is accessible via the New Zealand Police Intranet.
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AMI technology
This section contains the following topics:
• The technology
• Approved models
• Servicing
The technology
An AMI has three integral components:
• An electronic clock.
• At least one internal accelerometer.
• A microprocessor.
Note: The unit may have a read-out display and may be able to download data to a
computer.
AMIs used by Police must be set to provide data output in metric units and to show
acceleration as percentages of the force of gravity. The acceleration of gravity is that
measured at 45 degrees of latitude, 9.807 metres per second per second, commonly
expressed as 9.81 m/s2.
Approved models
Approved models are:
• The Vericom™ brake-testing computer Model VC2000 and VC 2000 PC (approved as a
brake-testing device on 18 October 1995; approval published by notice in NZ Gazette,
26 October 1995, Number 122, page 3775 (word document, 214 KB)).
• The Vericom™ brake-testing computer Model VC3000 (approved as a brake-testing
device on 18 March 2003; approval published by notice in NZ Gazette, 27 March
2003, Number 30, page 847).
Where the accelerometer used is a Vericom™ device, the manufacturer’s ‘Profile’
software is approved to be used for the data extraction, graph compilation and related
processing.
Servicing
All servicing and repairs must be arranged via Manager: Crash Investigation and
Calibration Services , Police Calibration Services, Ngauranga, Wellington.
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The controlled document can be found in the Police Instructions site which is accessible via the New Zealand Police Intranet.
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Training
This section contains the following topics:
• Approved training course
• Training in the use of AMIs
Approved training course
Approved training courses are delivered by Police and address the specific operation of
the AMI device concerned.
Training in the use of AMIs
To ensure national consistency and quality of content and delivery, all training must:
• be approved by the National Manager: Road Policing; and
• comply with the quality assurance standards set by the School of Patrol & Operational
Policing, RNZPC.
Approval of AMI instructors rests with the National Manager: Road Policing.
This is an uncontrolled document printed for reference only.
The controlled document can be found in the Police Instructions site which is accessible via the New Zealand Police Intranet.
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Duties and responsibilities
Table
This table shows the duties and responsibilities in respect of AMIs.
Position
Duties and responsibilities
District Commander District commanders must ensure that all Police employees
using AMIs are trained and deployed in accordance with this
chapter.
Supervisor
Supervisors of employees deployed to use AMIs must ensure
that:
• personnel under their control operate within the guidelines of
this chapter, and
• the equipment being used meets operational requirements
and that required repairs are carried out. See: Servicing.
Operator
Police employees who use AMIs must:
• be authorised to do so,
• have successfully completed the appropriate training course
and,
• have been issued with a certificate of attainment or,
• has previously completed any other form of training approved
by the National Manager: Road Policing
• have permanent appointment,
• have successfully completed the Advanced Crash
Investigation training course delivered by the School of Patrol
& Operational Policing, RNZPC, or equivalent qualification,
approved by the National Manager: Road Policing
• display the highest level of professional conduct,
• operate the device in accordance with this chapter, and
• be held responsible for their actions when operating the
device.
This is an uncontrolled document printed for reference only.
The controlled document can be found in the Police Instructions site which is accessible via the New Zealand Police Intranet.
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Pre-deployment check procedures
Pre-deployment check
A pre-deployment check must be conducted before each deployment of an AMI by
following these steps.
Step Action
1
Check that the date and time recorder (if any) within the accelerometer unit
has been correctly set.
2
Check that all related equipment is functional and in correct operating
condition.
3
Complete horizontal and vertical accuracy verification checks, recording all
results on the appropriate skid test data sheet.
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The controlled document can be found in the Police Instructions site which is accessible via the New Zealand Police Intranet.
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Deployment procedures
This section contains the following topics:
• Before you start
• Minimise disruption
• Evidence integrity
• Conducting tests
• Data accuracy tests
Before you start
Mount the instrument on the test vehicle in a position that meets the standard
requirements for operator and equipment safety, as well as the AMI device’s mounting
requirements.
Minimise disruption
Ensure that, as far as possible and reasonably practicable, the:
• tests are carried out with minimal disruption to other activities
• travelling public is inconvenienced as little as possible
• need for road closures is reduced or eliminated where possible
• tests are carried out as soon as possible after the incident took place.
Evidence integrity
Data collected using the AMI is recorded directly into the unit’s internal memory. Scene
data information from an accelerometer must be down-loaded using software approved
by the National Manager: Road Policing for the purpose.
Conducting tests
Follow these steps to conduct tests.
Step Action
1
Conduct at least three tests with an average acceleration force within a 10
percent range of each other. The acceleration force is shown on the AMI
readout.
2
Ensure that the tests are conducted in the same direction of travel as that for
the vehicle of interest.
3
For all calculations use the upper and lower values as determined from skid
testing.
Note: Do not use the average of all three tests.
4
When an acceleration graph is printed, the graph should show at least:
Where What
X axis (horizontal) Time
Y axis (vertical)
Speed, distance, g-force
Graphs for both the upper and lower ranges used should be produced.
Data accuracy tests
Follow these steps to conduct data accuracy tests.
Step Action
1
Check the speed obtained by the AMI against a calibrated speed-measuring
device. A result is satisfactory when the speed calculated by the AMI is within
10 percent of the calibrated speedometer reading, immediately prior to
braking.
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The controlled document can be found in the Police Instructions site which is accessible via the New Zealand Police Intranet.
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2
As an alternative to a speedometer test, you can check the distance reading
obtained by the AMI against the distance recorded by a pavement marker
activated by the vehicle braking system. A result is satisfactory when the
distance calculated by the AMI is within 10 percent of the pavement marker
distance, after appropriate adjustments have been made for mechanical
delays and the AMI activation setting.
This is an uncontrolled document printed for reference only.
The controlled document can be found in the Police Instructions site which is accessible via the New Zealand Police Intranet.
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After deployment procedures
This section contains the following topics:
• After the deployment
• Integrity of evidence
After the deployment
Follow these steps as soon as practicable after each deployment of an AMI.
Step Action
1
As soon as practicable after deploying an AMI, carry out all vertical and
horizontal accuracy verification checks.
2
A copy of the raw data relating to the skid tests must be retained with the
incident file.
Integrity of evidence
Scene data information from an accelerometer must be down-loaded using software
approved by the National Manager: Road Policing, for that purpose.
This is an uncontrolled document printed for reference only.
The controlled document can be found in the Police Instructions site which is accessible via the New Zealand Police Intranet.
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