Guidance

Frequently asked questions: Home Office type approval of road traffic law enforcement devices

Updated 18 December 2024

Applies to England, Scotland and Wales

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Any enquiries regarding this publication should be sent to us at: HOTA-Submissions@homeoffice.gov.uk

Version history

Version number	Purpose / Change	Date
1.0	Creation of a HOTA RTLED FAQ document	Oct 2024

Introduction

Scope

1.    This documentation is intended for participants in the Road Traffic Law Enforcement Devices (RTLED) Home Office Type Approval (HOTA) system (excluding equipment which is used to support law enforcement when assessing levels of alcohol and banned substances in drivers).

Purpose

2.    This document provides answers to frequently asked questions (FAQs) with HOTA RTLED. This includes FAQs relating to requirements detailed in The Speedmeter, Traffic Light and Prohibited Lane Enforcement Camera Handbook v2.0^{[footnote 1]}.

3.    It is the intention to incrementally add to this FAQ document at regular intervals, subject to questions being submitted.

4.    Feedback on the content of this document, including new questions for consideration or requests for further clarification, should be submitted to: HOTA-Submissions@homeoffice.gov.uk

Frequently asked questions

Section references are applicable to ‘The Speedmeter, Traffic Light and Prohibited Lane Enforcement Camera Handbook v2.0’.

1.    Within Section 5.1.2, Section 5.10.4 and others why is Network Time Protocol (NTP) not used for timing synchronisation of automatic distance/time speedmeters?

This requirement is there to make sure that automatic distance/time speedmeters can accurately read the speed.

Radio signal includes Global Positioning Systems (GPS), therefore this is acceptable to use for timing synchronisation of automatic distance/time speedmeters.

NTP cannot be used for timing synchronisation of automatic distance/time speedmeters as it is not accurate enough for the requirement, its latency is also more than GPS.

2.    Within Section 5.1.4, Section 5.11.5 and Section 7.6 why is there a requirement for average speed cameras to have the same geometry on entrance and exit/baseline correction factors?

The requirement for average speed cameras to maintain identical geometry at both entrance and exit points is crucial for accurately detecting vehicle positions based on using the vehicles number plates. This is because the system assumes the number plate is at a given height (e.g. 1 m). If the height of the number plate differs and the camera angles at the entry and exit points are not the same the system will view the number plate from different angles and the system will infer different distance offsets at the two positions. For short baselines this offset difference can be significant and cause speed measurement problems. If the geometry is identical the offset will be identical at both entry and exit therefore there will be no distance error. Hence the requirement is for the same geometry on entrance and exit/baseline correction factors.

3.    Within Section 5.9.2 why is encryption needed as soon as the information is acquired?

Evidential data should be encrypted without undue delay, meaning as soon as possible without any intentional delay, to ensure the integrity of the data. This is required to protect against unauthorised access and tampering.

4.    Within Section 5.9.3.1 why is AES 128 and AES 192 used?

AES 128 and AES 192 are still state of the art for attacks by classical computers. AES, particularly AES-256 is quantum resistant but not quantum secure. However, due to the nature of technology evolving encryption standards will be monitored and updated when the time comes.

Whilst the handbook recommends CMAC, HMAC is also acceptable.

5. Within Section 9.1 what is part of HOTA and what is outside of HOTA?

The OVDS hardware is not part of HOTA, but the OVDS software is part of HOTA.

 6. Within Section 5.9.5.1 where are commands generated and encrypted?

Commands are generated and encrypted on the OVDS.

7. Within Section 3.2 why is the Ingress Protection (IP) rating set to IP55?

Beyond a certain point, IP coding is not cumulative. Chapter 6 (pp 16-17) of the BS EN 60529:1992 says: ‘An enclosure designated with second characteristic numeral 7 or 8 only is considered unsuitable for exposure to water jets (designated by the second characteristic numeral 5 or 6) and need not comply with requirements for numeral 5 or 6 unless it is multiply coded.’

8. Within Section 7.1 why is the RADAR bandwidth/power set to these limits

The RADAR bandwidth is set to be within the protected bandwidth for emergency services. There are NO plans for this to expand as there would be risks in going outside of this into other RADAR bands that are used for other equipment.

RADAR frequency for Speedmeters has always been restricted to 24.1GHz +/- 25MHz. However, there has been a case-by-case basis allowance of the full emergency services bandwidth of ±50 MHz IF there is no danger of spill over.

The RADAR power is set to 5 mW/cm2 for safety and for interoperability with other equipment.

9.    Within Section 9.1 why is there a requirement of up to ±1 mph for speed simulators?

The ±1 mph requirement is there to make sure that speedmeters/speed simulators can accurately read the speed and keep within the confidence levels required for accuracy.

10. Within Section 9.4 speed measurement why is there a requirement to provide 500 measurements?

The purpose of this requirement is to ensure that the speedmeters can accurately read the speed. This recommendation comes from the OIML (OIML R 91 Edition 1990 (E)) and is standard on the continent. This specifies: “For pattern approval, 500 measurements shall be made, of which none shall give a positive error larger than + 3 km/h (or + 3 % at speeds above 100 km/h). Results that are recognizable as faulty by any user familiar with the handbook shall be discounted. If fewer measurements are made, they are to be considered as a sample which, by its result, shall validate the same error limits as would 500 measurements.”   For fewer measurements this means that in order to reach the confidence level interval of 99.8% the deviation of the measured speeds from actual speeds (or simulated speeds for lab tests) would need to be less. This means that accuracy becomes a more important consideration for smaller sample sizes. It is under these circumstances that a reduced sample might be accepted. This would need to be discussed with the HO on a case by case basis.

The 500 measurements requirement is also the same total that applied prior to 2017: 100 for the test house as indicated in ‘The Speedmeter Handbook (Fourth Edition 2005)’ and 400 for the ACPO police tests, for a total of 500.

Where a measurement mode is potentially different, i.e. using a different or an altered functionality, different direction, different geometry or stressing the measurement in some way(s), it may be necessary to treat this mode like a different speedmeter.

11. Why are device modifications required to go through a HOTA assessment?

Any modifications that might impact the rest of the equipment must receive approval. As an example, if the device changes from a wired to a wireless connection, the electromagnetic environment and potential susceptibilities change. Such a change must be evaluated to assess the effects on system performance and compatibility.

Home Office are reviewing a streamlined process for RTLED modifications and will advise further if any such process is introduced.

12. What is the purpose of the RTLED HOTA ‘balanced meetings’ which have been spoken about by Home Office?

Home Office see these meetings as being an opportunity to better understand specific process difficulties first-hand between individual stakeholder partners and government (Home Office and Dstl), on specific topics.

Requests for these meetings are balanced with the delivery of both business as usual and the assurance change programme, and are held at Home Office’s discretion.

Meeting terms of reference are available on request via HOTA- Submissions@homeoffice.gov.uk.

13. What is the role of Home Office and Dstl in the RTLED HOTA process?

Dstl are the Home Office’s technical partner and provide advice on the suitability of new or modified devices for HOTA to Home Office through the evidence provided by the applicant (e.g. test reports) during the application process. They also support the Home Office by advising on the Handbook.

The Home Office are responsible for the assurance of equipment used in frontline policing and other operational environments. For RTLEDs, the Home Office are responsible for making the decision on whether the equipment is suitable for type approval and issuing HOTA.

Home Office administrate the type approval process, from the receipt of submission forms through to the communication of the type approval decision.

Further information on the activities performed in the RTLED HOTA process can be found in HOTA of RTLED Submission Process Guidance (Appendix B).

End of document

1. The Speedmeter, Traffic Light and Prohibited Lane Enforcement Camera Handbook v2.0. A guide to type approval procedures for devices used for road traffic law enforcement in Great Britain. 19 December 2022. Collision reduction equipment (publishing.service.gov.uk) ↩