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Taxi Camera Systems: Six Questions You Need to AskMarch 2009 – VerifEye Technologies Incorporated

Introduction

Taxi regulators recognize the benefit of in-vehicle cameras as aneffective way to improve driver and passenger security. Thenumber of jurisdictions that have adopted a camera rule has

expanded steadily since the late 1990s, and that number

continues to grow. The reason is simple: taxi cameras work.

Whenever a licensing authority pursues a taxi camera safety

initiative, there is a need to determine formal requirements forthe evaluation of candidate camera systems. Not all systems are

equal. But a thoughtful evaluation process will spare the

embarrassment and expense of authorizing products not well-suited to the taxi

application.

How can a licensing authority do its best to develop technical specifications for a camera

system? What are the key questions to ask in the process of deliberation? This paperoutlines six questions that will help in the creation of proper requirements for a camera

system. These questions aren’t unique to any one city or jurisdiction, or to any particular

product. They are questions that arise frequently in response to the analysis of applicationneeds, and an appreciation of current technological and cost constraints. Whether they are

creating a new system specification, or updating an existing one, decision-makers, taxi

operators, and police will benefit from asking these questions.

1. Does the System Survive in the Taxi Environment?

Taxis present a particularly

demanding operating

environment for on-boardelectronic equipment.

Consider why: taxis are used

virtually ‘24/7’; they aremaintained at irregular

intervals; they feature a range

of electronic subsystems(data terminals, radios, meter,auxiliary lights, GPS, etc.). It

is worth noting that transit

systems are not always cross-compatible: a system that works in a bus or train, forinstance, may prove unsuitable for a taxi. The characteristics that should be specified to

ensure compatibility with the taxi environment include the following:



even in darkness. A supplementary IR illuminator (usually integrated in

the camera body) is used because the nearly invisible light doesn’t distractthe driver, but provides enough light to form an image on the camera

sensor. The illuminator must provide sufficient illumination power for the

camera, though not so much as to pose an eye-safety hazard. Monochrome

sensors are more sensitive to near-IR than colour sensors, and are usuallypreferred. When a colour sensor is used, it is important to ensure that the

filtering and lens coatings that are often used in colour imaging arecompatible with the near-IR requirements; without compatibility here,

image quality in dark conditions will suffer.

• System Resolution: The combination of lens, sensor, digitizer and imagecompression engine determines the system’s overall resolution – that is, its

ability to capture the subtle details of a scene or object. It is not enough to

merely specify the number of pixels contained in the captured image, as issometimes implied by the term “resolution”. Technical standards for

CCTV surveillance systems often contain visual test charts to quantifysystem resolution capability.i,ii These tests must cover the various lighting

conditions encountered in the use of taxis.

• Recording Frame Rate and Duration: Though it is technically feasible torecord several images per second for each camera, limiting average frame

rates allows for longer recording time. Experience suggests that arecording time of three or four days of operation is usually enough to

guarantee that incident recordings remain available to investigators. A

frame rate of one image per second is usually more than sufficient tocapture essential features of a criminal incident. As the capacity relative to

cost of solid-state memory technology improves, the recording frame rateand duration may be revisited.

• Event-based Recording: A system equipped with an event-based recordingscheme will record at higher frame rates before and after door openings or

panic button triggering. At other times, the recording rate is lower tomaximize recording time. Event-based recording (with pre-alarm

capability1ensures a higher recording rate when it is most likely to be

needed.

3. Does the System Protect Right-to-Privacy?

The proliferation of camera surveillance systems in public spaces has led to legitimateconcern over infringement of people’s privacy. Most jurisdictions have privacy laws, and

1“Pre-alarm buffer” refers to a technique whereby a fixed number of video frames are constantly recorded

so that they are available if required to provide the “history” just prior to the trigger. Driver risk

management systems always have a pre-alarm buffer feature (usually ten to twenty seconds). When used in

security systems they tend to be longer (e.g. minutes)



some authorities publish formal guidelines for the proper use of surveillance

technology.iii

One recent and disturbing trend is the large number of surveillance videosturning up on the internet via websites such as YouTube.com. This is an inappropriate

use of recording technology: the public can reasonably expect that a taxi’s interior is a

private space, and that occupants’ actions and conversations won’t be monitored or

distributed on the internet.

The trouble is that many “would-be” taxi camera products have no effective form of dataaccess control—meaning that the recordings can be viewed and copied by anyone with

physical access to the system. The potential unauthorized uses and abuses of surveillance

recordings are many: voyeurism to vigilantism to extortion. An appropriate candidatesystem should satisfy these basic privacy requirements:

• Recorded data should not be stored in an “open” or “standard” format (e.g.JPEG, MPEG, etc.) unless it is protected against unauthorized access witha proven secure encryption or coding scheme. Proprietary (specialized)

file formats are preferable because they can’t be opened by commercially-available video viewing and editing programs.

• The system must use a data access control method that’s impossible toshare or duplicate. By this standard, user/password and card/PIN-number

methods of access control come up short: cards and pass codes can be

shared and duplicated and can proliferate. Non-duplicable hardwaresecurity keys have proven to be practical and effective when responsibility

for key access can be managed by the proper authority. Biometric methods

(e.g. fingerprint scanning) may also be acceptable.

• The system must not include features such as an accessible “video out” jack and “rewind/play” controls that allow unauthorized users to review or

re-record stored data.

• All recorded data should be stored in a “first-in/first-out” buffer such thatany recording is eventually overwritten by newer data and is effectively

destroyed.

• “Covert” cameras, either hidden or disguised, must not be used, and signs

should be used to inform occupants that they are being recorded.

4. Does the Recorded Data Stand Up in Court?

Although many mobile camera systems are available, not all can collect data that issuitable for criminal investigation and prosecution. Some systems, for instance, are used

by the vehicle fleet operator to guard against fraudulent injury claims made by

passengers. Other systems are used to provide feedback during driver coaching. Forapplications like these, data security and chain-of-evidence is not an issue. Taxi camera

systems, on the other hand, are generally accessed for their recordings only in the event



of a serious crime. Chain of custody of evidence protocols must be followed if the data is

to be admissible in a court of law. Importantly, that these considerations are independentof those mentioned earlier with respect to privacy protection. This leads to the following

required characteristics and features:

• Source Identification: Recorded data must be stamped with a unique andunambiguous label identifying the camera recording device, taxi number

and taxi company, plus accurate date and time. In some jurisdictions, GPS

location coordinates are alsorequired. All of this

information must remain

attached to the recording andcopies of the recording.

• Unauthorized Data Access

Prevention: The system must

support an effective means of access control to prevent access

by unauthorized persons atevery link of the data handling

chain. A solution here is a

unique, non-duplicable

hardware key to download dataor review archived data.

user/password-based access isn’t effective given that pass codes may be

shared by several people and cannot be controlled.

• Data Completeness: In some jurisdictions it is required to be able to showthat data used in evidence is complete—that all of the data from the time

frame of interest is presented, that none was “edited out” of the sequence.

• Tamper Resistance: It is notoriously easy tomodify standard digital image formats such as

JPEG in ways that can be visually convincing(e.g. PhotoShop editing). The system therefore

must include an effective means to guarantee

the integrity of the original recording. Forexample, the use of proprietary, encrypted or

encoded file formats can be an effective guardagainst image tampering.

• Data Access History Auditing: Some jurisdictions place restrictions on thecircumstances under which recorded data may be accessed. The system

should therefore support a logging function that keeps a non-erasablerecord of when data access was made, by whom and for what purpose.



5. Can the System Monitor and Report Functional Problems?

Even well-designed equipment can fail. So when it fails, the person responsible for the

system and its repair must be alerted. “Hidden failures” are unacceptable in a system

intended to provide security—following a serious crime, no one wants to discover the

camera wasn’t working. Does the candidate system indicate failure for every potentialcause of trouble? That question is hard to answer with certainty, but the following list of

features serves as a minimum requirement:

• System Status Indicator : A statusindicator shows the user that the system

is either working normally or that it isfaulty. The status indicator signal must

not be too complicated. Users may be

trained to interpret a few indicator codes, but they won’t remember dozensof different ones. It’s best to keep it simple: for example, use of “red” to

indicate “alarm” and “green” to indicate “normal” is easily remembered.A flashing pattern for any colour may be used draw the user’s attention

and to indicate particular states. The status indicator must be in clear viewof the user. If the status indicator shows no light at all, that condition must

also be considered as a system failure.

• System Heartbeat Monitor : A “heartbeat” is a signal produced by asubsystem that indicates that it is functioning properly – for example,

writing image data successfully to memory. A heartbeat monitor is an

independent subsystem that “listens” for the heartbeat. If it ever loses theheartbeat signal, it may resuscitate the system (e.g., by restarting) and/or

activate a fault indicator.

• System Self-Diagnostics: The system should have built-in way to monitorinternal states and flag any abnormal conditions. A range of the system’s

features need to be monitored. (Does each camera circuit indicate a valid

camera signal? Does the storage memory return frequent “read or write”errors? Are power supply voltages within nominal range? Is the supply

current within nominal range? Is the real-time clock in synch with the GPS

clock? Is the GPS showing a valid signal? And so forth.) By monitoringkey functions, potential failures can be detected – hopefully before system

performance is compromised. Although these flags are not reported to the

equipment user, they should be available to qualified service techniciansthrough a computer interface and diagnostic software.

• System Inspection Function: Automated self-diagnostics, while important,are no substitute for periodic inspection by a qualified technician. The

system must be designed to support rapid inspection of functions such asimage capture, camera alignment, illuminator function, power-save

function, trigger capture, vehicle I.D., clock function, etc.



6. Is the System Resistant to Vandalism, Tampering and Theft of Stored Data?

The system should be designed with the

expectation that it will be subject to

mistreatment, either accidentally or not.Some jurisdictions, for example, require that

the system memory survive a car fire andsubmersion in water—unfortunately, there

have been cases where criminals have tried

to destroy the vehicle (and the evidence)following their crime. While not all

technical specifications will include this

provision, the following requirements would

be expected as a minimum:

• System storage memory must behoused separately from the

camera head(s) so that it can behidden from view. (Criminals

sometimes steal the camera head,

thinking it contains theincriminating evidence. Moral of

the story: don’t store the data in

the camera head!)

• All mechanical adjustments should be lockable so they can’t be altered

without the use of non-standard tools (e.g., security fasteners).

• Equipment housings should be inaccessible to unauthorized persons (e.g.use of security fasteners).

• All cable connections should require the use of specialized tools todisconnect.

• Power wiring connections and fuse should be inaccessible to

unauthorized persons, and it should be impractical for users to removepower to the unit.

• Equipment exteriors must not include any controls (e.g.“play/stop/rewind” buttons.)

Conclusions

This paper has explored six key questions that are critical to ask about any potential

camera system for use in a taxi security application:



• Does the Equipment Survive in the Taxi Environment?

• Is the Quality of the recorded Images Acceptable?

• Does the System Protect Right-to-Privacy?

• Does the Recorded Data Stand Up in Court?

• Can the System Monitor and Report Functional Problems?• Is the Equipment Resistant to Vandalism, Tampering and Theft of Stored Data?

Not all products that purport to be “taxi cameras” address these questions satisfactorily—

in fact, the majority do not. It is possible, though, to identify systems that are up to the

task, and rule out those that aren’t, using a proper specification and equipment approval

process. The requirements reviewed here can serve as a useful guide to creating orupdating a taxi camera specification.

iPerformance Testing of CCTV Perimeter Surveillance Systems (Using a Rotakin

Standard Test Target), Home Office Police Scientific Development Branch, Police PolicyDirectorate

ii2006 Australian Standard Closed circuit television (CCTV) Part 2: Application

Guidelines AS 4806.2

iii CCTV Code of Practice, January 2008, Information Commissioner’s Office,

www.ico.gov.uk

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