Taxi!

                        An Estimator for Taxi Fares
                                Version 1.0
                                     
                              Kevin Northover

Taxi! is  a utility  to  estimate taxicab  fares  given an  estimated  road
distance (for example from Mapper3a/London)  and an assumed average  speed.
It uses a  database file that  is easily  modified with the  built in  Data
application so you can add your favourite (or least favourite depending  on
costs!)  cities.  London and New York are included.

The motivation  for  writing  Taxi!  came  from  using  Steve  Litchfield's
excellent, now  sadly withdrawn,  Mapper3a/London and  taking lots  of  cab
rides while on a business trip to London.

You use Taxi! entirely at your own risk.  It is only an estimator and local
conditions (and  drivers) can  cause fares  for the  same journey  to  vary
significantly from day  to day.    My experience  suggests that an  average
speed between 7 and 10 miles per hour gives plausible estimates for Central
London journeys of around 3 to 4 miles.

Taxi! is placed in the public domain, you are free to do what you like with
it.  If you find it useful and add more cities I'd appreciate a copy of the
database entries.

INSTALLATION and USE

There are three files that should be installed:

TAXI.OPA       in a \APP\ directory on any drive
               this is the application, a Type 1 OPA
TAXI.DBF       in a \OPD\ on any drive
               this is the cities database
HAILTAXI.DBF   [Optional] in a \OPD\ on any drive

               this sets up your startup and defaults

Then install the icon using Psion-I from the system screen.

Taxi! puts up  two dialogs,  one to  enter the  journey specification,  the
second to report  the estimated  fare and any  extra information  available
(see Cities Database).  Keying Enter continues the program,

Esc terminates it.

STARTUP and DEFAULTS

Taxi! has three levels of default, controllable by the user:

   1 None: if Hailtaxi.dbf  is not  present then  the first  record in  the
     Taxi.dbf file sets the initial city and distance measure.  The program
     defaults to a journey of 2 miles  at 9 Mph. The user will be  prompted
     to confirm these.

   2 Default: if Hailtaxi.dbf contains only one record, then that sets  the
     defaults for the initial prompt.

   3 Startup: if  Hailtaxi.dbf  contains more  than  one record:  the  last
     record will  be used  to specify  the journey,  the user  will not  be
     prompted initially  for  journey  details; a  fare  estimate  will  be
     calculated and displayed; and the record  will be deleted.  This  mode
     is intended for invoking the program from another application.

Hailtaxi.dbf is a simple database , an example follows:

City:        London
Distance:    3
Speed:       9
Distance in: Miles

Distances can be handled in either Miles or Kilometers (Kms).  The  program
displays in the units set by the default processing.

CITIES DATABASE

The database  contains the  tariff  schedules for  the  taxi meters.    The
entries should  be  fairly  self-explanatory from  looking  at  the  London
example, however the format makes use  of tab delimited sub-fields to  make
the data entry  layout easier to  scan and  check.  (Enter  the tabs  using
Ctrl-Tab in Data.)  Data field names, and explanatory notes follow.

City:                   City name
Currency:               local currency symbol
Distance in:            Miles or Kms
Number Fare Bands:      number of different meter rates 1 <= n <= 3
Band Rates per Tick:    fare increment on meter for each band
Band Times per Tick:    maximum time between meter ticks (secs)
Band Distance per Tick: maximum distances before fare increments  (in
                        units specified)
Maximum Fares for Band: cumulative fares  before  switching  to  next
                        charge band;
                        set the last sub-field to a large number!
Extras:                 up to six lines of additonal data to be displayed
                        either as a single string or 2 sub-fields
                        Look at the the  London and New  York cities to  see
                        how this works
                        ...
Notes:                  ignored by the program



ASSUMPTIONS and RESTRICTIONS

The program and  database assume that  meters all work  much the same  way.
The number  of fare  bands is  limited  to three,  change the  #define  and
retranslate to modify this.

There is a  limit of  about 25  on the number  of cities  the program  will
handle; this  is determined  by the  maximum length  (255) of  the  dCHOICE
string.  However 25 should be more than enough for most travelers.

ACKNOWLEDGEMENTS

Andy Clarkson for OPP and OPPDBG.   Steve Litchfield for Mapper3a,  without
those distance estimates Taxi! would be much harder.