GPS & A Taxi Driver In Peril


Where In The World Are You?

by Terry Smythe
Secretary & General Manager
Manitoba Taxicab Board
Winnipeg, Manitoba, Canada
September 1992


On 27 September 1989, Winnipeg taxi driver Paramjit Singh was murdered by David Warriner, later convicted of the crime. It is now known that Mr. Singh was alive for some 15 minutes after he successfully triggered his emergency alarm. His dispatcher, colleagues and police all knew he was in trouble, but nobody could find him. His last known location was at the bus depot in the heart of the city, from where he accepted a trip from David Warriner who directed him to take a certain route out of town, but without a destination. He died beside his taxi.

The circumstances of his situation, seemingly insurmountable at the time, are now being presented with a fine opportunity to summon help most immediate with the help of satellite navigation, otherwise known as (G)lobal (P)ositioning (S)ystem (GPS).


How a Satellite Guides You For a number of years, the U.S. Department of Defense has been lofting a series of navigation satellites in orbit around the earth, at an altitude of approximately 11,000 miles. When fully deployed, 24 satellites will be on station. 19 are now in orbit, and they are equally spaced in three orbital planes such that at least 3 are in line of sight to a specific location anywhere on the face of the earth.

Each of these satellites continuously transmits a uniquely coded navigation signal. The process is entirely passive. No signal is needed from a ground based receiver to make use of it. This passive approach can therefore accommodate an unlimited number of worldwide users, at no cost to each of the users of the signal.

The GPS black box mounted in the trunk, no bigger than a good book, has the ability to receive these navigation signals from the array of satellites in line of sight and instantaneously calculate its position by triangulation in terms of precise latitude and longitude on the face of the earth. To be useful to the taxi industry, this signal must be transmitted to a base computer, typically riding on the carrier of the vehicle's voice radio. The base computer then takes over by translating the latitude/longitude signal into a specific location on city streets, displaying it as a moving miniature vehicle (icon) on a computer screen.

A single location signal is of limited value, but a stream of these signals flowing into the base computer, provides the ability to track the precise movements of a taxi with a driver at the wheel in fear of his life, following the commands of his assailant in the back seat.


Taxi drivers have become the focus of an awesome array of mayhem inflicted upon then, and it is important to review some circumstances contributing to this situation, and to the risk factor. In the early 30's in most jurisdictions, the taxicab industry was properly seen as an important, integral part of the public transportation system, a public utility. As a public utility, it became a regulated industry no differently than any other public utility. Up to the mid 60's, the industry was generally organized along traditional corporate organizational lines. The companies owned the vehicles, employed the drivers, measured the demand and had control. Throughout this time, the industry basically supervised itself.

However, at about this time, the industry started migrating into the "independent owner-operator" organizational structure, and major long term problems with the industry emerged. In 20/20 hindsight, it is clear that most regulators did not foresee the long term consequences of these problems, and in many cases inadvertently nourished and contributed to the growth and perpetuation of these problems to this day.

This focus on "independence" has emerged over the years in response to economic pressures provoking the industry to find creative means to cut costs and increase revenues and margins. "Employees" are subject to legislation requiring overhead expenditures related to pensions, income taxes, health insurance, sick pay, vacation pay, etc. "Independent contractors" are considered to be a self-employed business and consequently exempt these expenditures. The critical ingredient is the amount of control exercised over the drivers by the company. So long as control is minimal, their independent status is preserved. The "independence" issue is critical to driver safety.

In trying to determine just how risky is the life of a taxi driver, it is extremely difficult to reduce the situation to statistical indicators for this kind of data is just not available. Government databases often do not specifically track incidents relating to the taxi industry, because their source of such data is from the files of Worker's Compensation, which does not yield data specifically identified to the taxi industry, because "independent contractors" do not contribute to Worker's Compensation, and so do not enjoy the benefits of claims. In Canada, StatsCan was recently approached for this data and they reported only 28 such incidents in the whole of Canada in the whole of 1991! Similar inquiries to local and national police forces similarly failed to produce the needed data. However, a scan of major newspapers reveals that taxi drivers are the focus of an awesome array of mayhem, including murder. Police forces are reporting a clear sign that tough economic times have over the past few years provoked a noticeable increase in break-ins and robberies. Hard statistics are difficult to acquire because the acceleration of incidents is faster than the data collection processes. However, the indicators are clear that there is a sharp increase in risk levels facing taxi drivers and even the police themselves.

Historically, the taxicab industry has been cash based. As a consequence, there is a widespread perception that a taxi driver is an easy mark for robbery, and substantial dollars will emerge as proceeds of the criminal action. However, over the years, the industry has been migrating to the elusive "cashless taxicab", largely through credit card operations. The amount of cash that a typical cab driver carries is now less than previous. However, this is not yet widely known and robberies still occur, but have been reduced to senseless criminal acts typically resulting in proceeds of less than $50.


A major weakness of taxi driver safety has been that a driver's work station is not stationary. It moves around, and if a driver is in trouble, the ability to bring help to him quickly is not now possible. It is absolutely critical that help be converged on a driver in trouble within a scant few minutes. To do that, it is absolutely imperative that his precise location be pinpointed the instant a driver in peril triggers his emergency alarm.

Historically, a number of emergency location systems have been developed, but all have been land based technology. Their fundamental shortcoming has always been that the instant a driver strays outside the range of the system, his location is no longer identifiable. Such systems are inherently expensive.

As a direct consequence of the Desert Storm War, GPS received an extraordinary boost, and emerged from the war at a dramatically reduced cost. GPS has been in use for aircraft in the sky and ships on the high seas for several years, but it is only recently that a number of manufacturers have identified vehicles on the ground as a mammoth market opportunity.

One such supplier, Trimble Navigation in Sunnyvale, California, has already participated in 2 courier dispatch systems in the San Francisco area, a transit bus system in Denver, and is currently in the process of developing an Automatic Vehicle Location system aimed at the taxi industry. The focus is taxi driver safety. PulSearch in Calgary participated in a pilot patrol car dispatch system for the Calgary City Police. In August 1991, a target cost of $2,500 per vehicle was estimated for the GPS receiver alone. However, the rapidity of developments in the electronics industry was produced a dramatic reduction of estimated costs of a basic GPS Receiver to something in the order of $500-$600 ($US) in quantity.

This simplest of GPS systems, that having the sole purpose of broadcasting a location signal for a driver in peril, may be triggered by an emergency alarm switch. Only then would the signal be broadcast, immediately alerting his dispatcher, who in turn can immediately alert the police and his nearest colleagues. Even if the driver is directed under threat to drive an evasive pattern, a show of force can be quickly dispatched to his immediate surroundings, hopefully inspiring the surprised assailant to surrender peacefully.

At modest additional cost, triggering the emergency alarm can also initiate additional features aimed at minimizing the peril of a driver under an assailant's control. The taxi's voice reception system can be terminated, so that the dispatcher can "listen in" to what is going on inside the cab. Even if the assailant rips out the visible microphone, the dispatcher can still "listen in" through a second microphone hidden in the cab. Alternately flashing tail lights might also be triggered at the same time.


An immediate concern to any potential user planning to commit substantial resources, is the continuing reliability of the signal. These satellites were placed in orbit by the U.S. Department of Defense for military purposes. Their signals are open and freely available at this time. However, it would seem quite reasonable that by the throw of a single switch in times of international conflict, these signals could become instantly encrypted, useful only to military receivers capable of de-encryption.

Early into this program the Department of Defense stated that under certain conditions of high peril, the military may deny the availability of the more precise signals, supposedly to the enemy, but in reality to all. However, the less precise regular signal would otherwise be available to the civil sector. In his early analysis of this concern, Glen Gilbert in 1978 concluded:

"In summary, the discussion of the availability of the NAVSTAR GPS signal and more particularly the precise accuracy is mostly a political issue as opposed to a technical one. If the Federal Government as a whole were willing to advocate NAVSTAR GPS as a national resource, a relatively simple solution could be found to allay the "scare story" that the signal could be denied to the civil sector. Alternatively, it is clear that detractors from the civil use of the system will be obtuse about such practical solutions. Satellites will eventually be used as the primary source of radio navigation. Denial is a minor issue, if it is a valid issue at all."

In September 1991, Assistant Secretary of Transportation, Admiral James Busey IV, announced in Montreal at a major civil aviation conference that commencing in 1993, the U.S. Government will have all 24 satellites in orbit, and the signals from them will be made available to civil applications throughout the world at no cost for a minimum of 10 years. At a major demonstration of GPS in Washington, DC in April 1992, Admiral Busey restated the Government's commitment, and technical advisors added that the satellites will likely continue providing quality signals for 15 or more years. During this time, a follow-along system will be developed and lofted into space that is compatible to the existing world wide array of ground stations.


The basic elements of a minimum taxi driver safety alarm system are:

1. An Alarm Switch.

Being a simple switch, this is the least costly element of the system, but as it makes possible the entire sequence of events, it is important that its location and simplicity of covert operation be carefully considered. For modest additional cost, the switch could be wireless and shaped in the fashion of something quite innocent in appearance.

2. A Location Sensor (GPS Receiver)

Ideally, a 6 channel GPS receiver, outputting location, heading, speed, and time at least once per second. The basic requirement is for low cost, with 100 meter or better accuracy. For additional cost, it is possible to merge in additional sensors to simultaneously report other conditions, such as someone sitting in the back seat, an overheated engine, a system malfunction, etc.

3. An Intelligent Mobile Radio Modem

This is required to receive latitude/longitude data from the GPS receiver, and modulate it for transmission to the base receiver. These devices are quite different from conventional computer modems used in the conventional telephone network, as they must deal with a more hostile transmission environment of a moving vehicle in radio fading conditions. It must be intelligent enough to silently auto-dial a cellular phone, or alternatively link with the radio transmitter.

4. A Transmission Device

Ordinarily, this might be considered a radio within a trunk radio network, or a cellular phone. For the purposes of taxi driver safety, a cellular phone is preferred because of its relatively low initial cost, and reasonable connection fees. In theory, it would only be activated during an emergency, so cost of operation would be minimal. However, with a cellular phone already in the taxi, the driver has at his fingertips both a customer service device and a revenue generator. Experience in other cities has clearly revealed the presence of a cellular phone to be a profitable and desirable tool. It is highly recommended.

If, however, the taxi company chooses to use some form of radio as the data carrier, then the option of transmitting GPS data continuously, rather than emergency only, opens up a whole new cost effective fleet management consideration.

5. A GPS Antenna

Both the radio and the GPS receiver require antennas, and they are different. The radio antenna is ordinarily a short visible stick, but the GPS antenna has a unique shape. There are two schools of thought on whether the GPS antenna should be visible or covert. If visible, an assailant may see it, recognize it, and use strategic tactics to ensure it never gets turned on. Or, an assailant may see it, recognize it, and choose not to assault the driver knowing instant response will most certainly emerge as if by magic. The user should carefully consider the pros and cons, perhaps in consultation with local police forces.

All components described herein are in use now in one form or another. No development of significance is required. Following are potential costs as if installed in a single vehicle, or in 500 vehicles as a single order, or 500 vehicles about a year from now in consideration of anticipated dramatic cost reductions in this new explosive market opportunity. For this display, all prices are shown in $US.

Item			Unit Price    Qty 500	  Qty 500 in '93

GPS Receiver		$  950	      $  640	     $  450
Radio Modem		 1,000	         650 	        550
Cellular Phone		   250	         180	        130
Antenna & Installation	   350		 200		160

Total In-Vehicle Price	$2,550	      $1,670	    $ 1,290

Translation of the quantity capital cost into a 5 year lease agreement, results in a very favourable monthly cost per vehicle in the order of $60. The cost of a base computer is not considered here because of a reasonable presumption that the taxi company already has one appropriate to the needs. There would be an additional cost to acquire a digitized map of the local city, and the software needed to translate the latitude/longitude GPS data into a specific street location instantly. These additional costs would vary from one location to another, particularly if a number of dispatchers of taxicabs, couriers, maintenance vehicles etc., each acquire their own copy.


For the GPS receiver, it is no trick at all to calculate and report where it is. These satellites were first placed in orbit as far back as 14 years ago. The technology is not new at all, it is just new in identifying specific location of vehicles on streets. When reporting where it is, the GPS receiver does so in terms of latitude and longitude, and with great precision. However, for most of us, knowing where we are in terms of latitude and longitude is of small comfort if this cannot be related to a specific street intersection in a specific city.

What is needed for all cities is a digitized map with all streets and intersections cross referenced to their equivalent specific street address. Only with such a digitized map will latitude/longitude addresses become meaningful to the average person in a car or manning a dispatch station. The simplest of such maps, a street line map, is quite adequate for GPS purposes, and most every major city throughout North America has an efficient mapping group in its bureaucracy.

Desk top computer technology has now reached a level of sophistication and power that a conventional 486 based micro-computer, with a high capacity hard drive and a high resolution VGA colour monitor, is quite capable of satisfying the needs of not only a simple (A)utomatic (V)ehicle (L)ocation system, but a fleet management system tracking and administering to the needs of several hundred vehicles.

Because a GPS receiver requires several minutes to acquire at least 3 satellites overhead in line of sight, it must be in operation at all times in order to instantly transmit its specific location in an emergency situation, and continue doing so until the emergency is canceled. However, if the GPS receiver is indeed constantly calculating its whereabouts, it then becomes only one tiny baby step to migrate into fleet management by simply transmitting location continuously. A constant flow of GPS location data can form the basis of fleet management with awesome accuracy.

To accurately pinpoint a taxi driver in trouble and facilitate rapid dispatch of a helpful force of other taxicabs and police cars is a relatively trivial exercise of leading edge technology that really isn't leading edge at all. It is truly astounding that it has taken so long for the world at large to realize its simplicity and potential. There is no question that the processes of precision calculation of location are indeed sophisticated, but it is not mysterious.

It is not imperative that taxi regulators and taxi company managers have an intimate understanding of the nuts and bolts, and bits and bytes that make up the system. It is suffice that it works, and now does so in a cost effective manner. Accept it! Embrace it! Believe in it! It works, it's reliable, and offers outstanding benefits not only for a taxi driver in peril, but also taxi company management, and the taxi regulator. This truly is a 21st Century utility available now!


The GPS location data (longitude/latitude) calculated by the GPS receiver is of no value if it is not sent to the dispatch computer instantly. That data may be sent to the dispatch computer on the carrier of the voice radio already in the taxi, or a cellular link may be installed to use that network. Either way will work, although the frequencies of the voice radio network are becoming quite crowded in recent years as the demand for dispatch services increase. A more desirable approach is to use the cellular network to transmit the emergency signal to the dispatch computer. When this is done, the addition of a cellular phone itself is trivial. These phones are a marketing option of some considerable importance and additional revenue. The Las Vegas experiment proved that cellular phones in taxicabs can be a lucrative customer service. It should be aggressively embraced.


Following a series of taxi driver murders in Las Vegas in 1990, an electronics engineer there, Mr. Jerry Newton, President of Image Comm, designed and built an emergency system for the Las Vegas taxi industry. At its heart was a GPS receiver capable of receiving passive signals from GPS navigation satellites passing overhead, doing precision computations based on those signals, and reporting its location in terms of latitude and longitude.

The GPS receiver only receives a signal, it does not transmit. That function is satisfied by whatever voice communications system already exists in the vehicle. He elected to build into his system a cellular phone whose function was to carry the GPS signal in an emergency, but when not in use could be used as a revenue generator for a fee by customers. It proved to be a profitable marketing tool.

As a companion device to GPS, he built into his system a tiny still picture TV camera mounted above the rear view mirror. Within six seconds of a new passenger sitting in the rear seat, a wide-angle photo of all occupants was transmitted on the telephone carrier to the base computer where it resided peaceful and quiet until the next picture came along.

The instant a driver was in trouble and triggered his silent alarm, the GPS latitude/longitude signal was transmitted to the Las Vegas police department simultaneous with a photo of the occupants. The police were able to respond quickly, and identification was possible with the photos. On the few occasions when the system was triggered, it proved its worth and was successful. At a cost of some $4,500 per vehicle, it was clearly expensive. However, the presence of a cellular phone as a customer service revenue generator offset the cost.

Regrettably, the system Mr. Newton developed was not proceeded with because drivers resented the presence of the camera, claiming invasion of privacy. Following his own review of the situation, he later stated that drivers had told him they simply did not want a camera invading their privacy. Notwithstanding that the system was basically sound, the entire package was terminated, including the GPS portion of the system. In 20/20 hindsight, it would appear that the inclusion of a still TV camera was an elegant feature really not critical to the system.


Taxi driver safety has been a critical troublesome issue for many years. The mobility of his work station, coupled with the absence of demand sensitive service levels as a consequence of the independent owner-operator organizational structure, tend to place a typical taxi driver in a risky work environment. Over the years, a number of potential solutions have been repeatedly examined with moderate success.

One such example are safety shields for taxicabs. There has never been a prohibition against voluntary installation, but their continuing absence is very clear evidence that a majority of drivers sincerely believe that safety shields will intrude into the provision of good service. Furthermore, since the Checker Cab Co. went out of business in the early 80's, the taxicab industry has been deprived of good vehicle specifically designed for its needs, including a safety shield integral to the driver's bench seat. The industry has had no option but to progressively migrate into the use of conventional 4 door passenger cars as the primary vehicle for taxi use. Unfortunately, the conventional 4 door family car has been shrinking steadily in size, such that it is no longer possible to insert a safety shield between the passenger and the driver due to insufficient leg room.

While no viable solution has emerged to separate a driver from his customers, a way has been found to specifically and instantaneously pinpoint the location of a taxi driver in peril. It matters not that the driver may not follow all the rules for his own safety and survival, for GPS will instantly broadcast his location with great accuracy, making it possible for appropriate emergency response systems to swing into high gear and quickly bring help to him, no matter where he is or where he is traveling. The probability of successful survival of an assault, robbery, or theft of the taxicab is dramatically enhanced by the use of Global Positioning System. It should be embraced with enthusiasm and commitment.

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