4.3 Warning illumination patterns and preliminary DVI design review
study

4.3.1 Goal of the study

To obtain operator feedback on four different DVI warning illumination
methods and on where optimal warning threshold onsets should be set.

4.3.2 Method

In this session PATH researchers met with operators and trainers in a
meeting room at the SamTrans Maintenance Yard in October 2001. The
operators and trainers were given a background of the FCWS program and
shown pictures of what the DVI would look like both physically and
installed on the bus. The operators were given an explanation of
Time-To-Collision (TTC) and the circumstances under which the display
may be of assistance to them. Operators were then shown a working
simulated version that depicted a bus driving from the bus operators'
perspective (Fig. 70) with four different warning illumination methods
(Table 22 and 23). In addition to the different warning illumination
patterns operators were shown different warning activation thresholds.
The simulation was run for as long as was requested by the
operators/trainers on each of the display/timing combinations.

  -----------------------------------------------------------------------
  ![](media/image1.wmf)

  Fig. 1 Simulated FCWS DVI
  -----------------------------------------------------------------------

####  {#section .LABEL}

+-----------------------------------------+----------------------------+
| Table 1 Top down illumination method    |                            |
+-----------------------------------------+----------------------------+
| The LED\'s are lit downwards from the   | Warning Illumination       |
| top as the TTC becomes shorter. The     | Description                |
| growing of the bars is intended to      |                            |
| mimic that the target range is becoming |                            |
| shorter and shorter.                    |                            |
+-----------------------------------------+----------------------------+
| ![](media/i                             | Multiple colors are        |
| mage2.jpeg){width="3.577777777777778in" | displayed as TTC gets      |
| height="2.3319444444444444in"}          | shorter. This scheme gives |
|                                         | a good feeling of warning  |
|                                         | grades as the earlier-lit  |
|                                         | LED\'s stay on the         |
|                                         | original colors.           |
|                                         |                            |
|                                         | The first three segments   |
|                                         | are yellow (going from top |
|                                         | to bottom), the next two   |
|                                         | are orange and the last    |
|                                         | two are red.               |
+-----------------------------------------+----------------------------+
| ![](media/im                            | One color is displayed at  |
| age3.jpeg){width="3.7333333333333334in" | a time. This scheme        |
| height="2.433333333333333in"}           | emphasizes the urgent      |
|                                         | warnings by changing the   |
|                                         | color of all the bars as   |
|                                         | TTC becomes shorter.       |
|                                         |                            |
|                                         | The first three segments   |
|                                         | are yellow (going from top |
|                                         | to bottom), when the next  |
|                                         | two segments light up the  |
|                                         | whole bar turns to orange, |
|                                         | when the last two segments |
|                                         | light up the whole bar     |
|                                         | turns to red.              |
+-----------------------------------------+----------------------------+

####  {#section-1 .LABEL}

+--------------------------------------+-------------------------------+
| Table 2 Looming illumination method  |                               |
+--------------------------------------+-------------------------------+
| The LED\'s are lit from the middle   | Warning Illumination          |
| to both the top and the bottom. The  | Description                   |
| growing of the bars is intended to   |                               |
| convey the sense that the visual     |                               |
| angle of the target is becoming      |                               |
| wider and wider.                     |                               |
+--------------------------------------+-------------------------------+
| ![](media/image                      | Multiple colors are displayed |
| 4.jpeg){width="3.7333333333333334in" | as TTC gets shorter. This     |
| height="2.636111111111111in"}        | scheme gives a good feeling   |
|                                      | of warning grades as the      |
|                                      | earlier-lit LED\'s stay on    |
|                                      | the original colors.          |
|                                      |                               |
|                                      | The center three segments are |
|                                      | yellow, the next two segments |
|                                      | (one either side of the       |
|                                      | yellow) are orange and the    |
|                                      | remaining two segments are    |
|                                      | red.                          |
+--------------------------------------+-------------------------------+
| ![](media/image                      | One color is displayed at a   |
| 5.jpeg){width="3.7333333333333334in" | time. This scheme emphasizes  |
| height="2.433333333333333in"}        | the urgent warnings by        |
|                                      | changing the color of all the |
|                                      | bars when TTC becomes         |
|                                      | shorter.                      |
|                                      |                               |
|                                      | When TTC is long the center   |
|                                      | three segments are yellow, as |
|                                      | TTC gets shorter if five      |
|                                      | segments are on the color is  |
|                                      | orange, if seven segments are |
|                                      | on the color is red.          |
+--------------------------------------+-------------------------------+

4.3.3 Feedback

Feedback from the operators indicated that the operators unanimously
preferred the top down mono-color illumination method, as this was the
least distracting/annoying and the easiest to interpret. There was some
concern over the yellow color with some operators reporting that they
found it irritating and were interested in the possibility of canceling
this color out. Some operators also reported that they did not associate
the color yellow with a threat or a warning. One operator wanted only
red to be used. The operators reported that the three colors made the
display too visually busy at a time when their attention was needed
outside of the bus.

The operators were reluctant to comment on the warning activation
thresholds as they felt that this really needed to be tested by driving
with a real system.

4.3.4 Outcome -- DVI Refinements

A decision was made to use the top-down mono-color warning illumination
pattern. It was decided that a decision on canceling out one of the
colors and determining optimum parameters for warning activation would
wait until the prototype system was tested on a bus.

4.4 Advisory committee meeting

4.4.1 Goal of the Meeting

To gather feedback from the advisory committee members on the FCWS
project progress.

4.4.2 Method

In December, 2001 PATH hosted a FCWS program review meeting for
operators, trainers and members of the advisory committee. At this
meeting attendees were given talks on the following subject areas: IVI
program status, program overview, and review of technical development,
algorithm development, prototype data collection system hardware, DVI
design considerations, DVI development, data analysis, data analysis
tools, integration project plan and given a demonstration. The
demonstration was conducted on a bus driving on both local and freeway
streets in the Richmond (California) vicinity with a working prototype
system on the bus.

After the demonstration feedback was collected from the meeting
attendees on the program in general as well as the DVI development. Only
the DVI development feedback will be discussed here.

4.4.3 Feedback

Feedback from this meeting was that:

-   The location of the display was deemed to be "perfect".

-   That the current DVI is too large. Operators would like to see the
    display reduced in both height and width "to about the size of
    Christmas tree lights" was a common comment.

-   Optimal sensitivity level(s) for when warning activation should be
    further refined.

-   That the radar or lidar sensor needed to work when the bus is
    stopped (if possible).

-   That three colors in the display required too much visual attention
    and that removal of the yellow color should be further investigated.

-   Night operators expressed concern at the amount of potential glare
    from the DVI. The night operators reiterated their request for an
    audible DVI.

4.4.4 Outcome -- DVI refinements

A decision was made to reduce the size of the DVI for the DVI to be
installed in the second bus and then to compare longer term operator
evaluations of the two different size DVIs. The DVI for the second bus
was reduced by approximately two thirds in length and consists of a
single row of seven stacked LED segments. In addition the yellow color
was removed from the DVI.

4.5 Test-Drive Study

4.5.1 Goal of the Study

To obtain test-drive operator feedback from the working prototype DVI.

4.5.2 Method

Six operators (one female and five males) were introduced to the system
in February 2002. Five operators attended two 1.45 hour sessions. One
operator attended only the first session as he was unavailable for the
second. The operators' bus driving experience ranged from 2.5 to 27
years with a mean of 14.1 years experience. One operator indicated that
they drove predominantly on day shifts, one on night and the other four
operators were extra board so drove both day and night shifts as
required.

The test drive sessions occurred over a four-day period with the second
session occurring after a one day break. The test drive sessions were
conducted in two blocks, the first block began at 10 am and the second
began around 4:30 pm finishing around 9 pm (we encountered some system
problems on the first day so the schedule ran on later into the
evening). The intention was to give drivers exposure to the system in
both daylight and lowlight conditions. All sessions began in the
SamTrans maintenance yard.

4.5.2.1 Session one

Each operator was first given an overview explanation of the FCWS, this
included how objects were detected, conditions that the system worked
well in and not well in and what the different display illumination
methods meant. The operators were then given a system walk-through; they
adjusted the display brightness and had their questions regarding the
system answered. The operators were then asked to drive the bus in the
SamTrans Maintenance Yard and approach stationary objects so that they
could see the system working, after which any further questions were
answered. The operators were then asked to drive on a local route that
they were familiar with (their normal route, if they had one). All of
the routes included both local streets and freeway driving. Operators
were asked to drive the way that they normally would, including pulling
into bus stops where it was practical and safe to do so. Operators did
not pull into bus stops where there were buses entering and exiting or
where there was groups of people waiting for a bus as we did not want to
frustrate and/or confuse SamTrans patrons.

A range of different warning thresholds were tried over the
approximately 1.5 hours of driving time.

At the end of each session the operators were asked questions about the
system. Responses to the questions can be seen in the table in section
4.5.3.

4.5.2.2 Session two

In the second session operators were encouraged to test the system in
any way that they were interested in order for them to see how the
system performed. This session took approximately 1.45 hours and again
was conducted on both local streets and on the freeway. Areas that
operators were interested to test the system on included a section
around San Francisco International Airport that was under construction,
as they wanted to see how it performed with the construction equipment,
concrete pillars and overhead roads, down narrow windy streets and to a
hospital exit that had a large dip at the bottom.

At the end of both sessions operators were asked for their feedback on
the visual DVI. Answers from both sessions are combined below.

Table 3 Operator Feedback of FCWS System

+------------------------+--------+-----------------+-----------------+
| Question to operators  | Number | Response        | Comments        |
|                        | of     |                 |                 |
|                        | ope    |                 |                 |
|                        | rators |                 |                 |
+------------------------+--------+-----------------+-----------------+
| Did the system         | 6      | "Yes"           | "It gave alarms |
| function the way that  |        |                 | close to the    |
| you thought it would?  |        |                 | distance I      |
|                        |        |                 | would stop at"  |
+------------------------+--------+-----------------+-----------------+
| Please describe any    | 1      | "Cars cutting   | "It doesn't     |
| instances where you    |        | in"             | always pick up  |
| felt you should have   |        |                 | cars cutting in |
| received a warning but |        |                 | soon enough"    |
| didn't?                |        |                 |                 |
+------------------------+--------+-----------------+-----------------+
| Can you describe any   | 1      | "Picking up     | "Is a problem   |
| instances where you    |        | reflective road | particularly in |
| received a warning but |        | signs"          | construction    |
| felt that you          |        |                 | areas"          |
| shouldn't?             |        |                 |                 |
+------------------------+--------+-----------------+-----------------+
|                        | 1      | "Picks up       | "Picks up too   |
|                        |        | parked cars in  | many parked     |
|                        |        | narrow windy    | cars on this    |
|                        |        | residential     | (particular)    |
|                        |        | streets"        | street "        |
+------------------------+--------+-----------------+-----------------+
|                        | 1      | "Off ramp guard | "This is        |
|                        |        | rails -- where  | dangerous at    |
|                        |        | the off ramp    | night as the    |
|                        |        | has a curve, it | light impedes   |
|                        |        | picks up the    | vision when     |
|                        |        | outside curve"  | need to be able |
|                        |        |                 | to see the      |
|                        |        |                 | outside curve"  |
+------------------------+--------+-----------------+-----------------+
|                        | 1      | "Sometimes if   | "This directs   |
|                        |        | on freeway and  | your attention  |
|                        |        | change lane to  | away from       |
|                        |        | the left lane   | looking over    |
|                        |        | it picks up the | your left       |
|                        |        | car in front on | shoulder to see |
|                        |        | right hand side | if the lane you |
|                        |        | as you go past" | are moving into |
|                        |        |                 | is clear" "This |
|                        |        |                 | is distracting" |
+------------------------+--------+-----------------+-----------------+
| Did you like the       | 5      | "Yes"           | "cool concept"  |
| system?                |        |                 | "help drivers   |
|                        |        |                 | to reduce some  |
|                        |        |                 | accidents" "get |
|                        |        |                 | their           |
|                        |        |                 | attention"      |
+------------------------+--------+-----------------+-----------------+
|                        | 1      | "Overall        |                 |
|                        |        | impression --   |                 |
|                        |        | concept (is)    |                 |
|                        |        | good -- but     |                 |
|                        |        | need            |                 |
|                        |        | audible         |                 |
|                        |        | /vibration/blue |                 |
|                        |        | light"          |                 |
+------------------------+--------+-----------------+-----------------+
| Did you find the       | 6      | "Yes"           |                 |
| system easy to use?    |        |                 |                 |
+------------------------+--------+-----------------+-----------------+
| Would you like to      | 5      | "Yes"           | "False alarm    |
| drive with the system  |        |                 | level seems --  |
| the way it currently   |        |                 | ok"             |
| is?                    |        |                 |                 |
+------------------------+--------+-----------------+-----------------+
|                        | 1      | "No"            | "I do not want  |
|                        |        |                 | a visual        |
|                        |        |                 | display"        |
|                        |        |                 |                 |
|                        |        |                 | "To many false  |
|                        |        |                 | alarms"         |
+------------------------+--------+-----------------+-----------------+
| How long do you think  | 1      | "No time"       |                 |
| an operator would need |        |                 |                 |
| to become comfortable  |        |                 |                 |
| with the system        |        |                 |                 |
+------------------------+--------+-----------------+-----------------+
|                        | 1      | "1 hour"        |                 |
+------------------------+--------+-----------------+-----------------+
|                        | 1      | "1 time         |                 |
|                        |        | driving"        |                 |
+------------------------+--------+-----------------+-----------------+
|                        | 1      | "A couple of    |                 |
|                        |        | hours"          |                 |
+------------------------+--------+-----------------+-----------------+
|                        | 1      | "A couple of    |                 |
|                        |        | days"           |                 |
+------------------------+--------+-----------------+-----------------+
|                        | 1      | "Unsure"        |                 |
+------------------------+--------+-----------------+-----------------+
| When did the system    | 1      | "Construction   |                 |
| provide you with the   |        | areas"          |                 |
| most assistance?       |        |                 |                 |
| (note: some operators  |        |                 |                 |
| indicated more than    |        |                 |                 |
| one response)          |        |                 |                 |
+------------------------+--------+-----------------+-----------------+
|                        | 1      | "Cut in's on    |                 |
|                        |        | the freeway"    |                 |
+------------------------+--------+-----------------+-----------------+
|                        | 2      | "With           |                 |
|                        |        | pedestrians"    |                 |
+------------------------+--------+-----------------+-----------------+
|                        | 1      | "In heavy       |                 |
|                        |        | traffic"        |                 |
+------------------------+--------+-----------------+-----------------+
|                        | 1      | "When operator  |                 |
|                        |        | is inattentive" |                 |
+------------------------+--------+-----------------+-----------------+
|                        | 1      | "When turning   |                 |
|                        |        | slowly"         |                 |
+------------------------+--------+-----------------+-----------------+
| If you could           | 6      | "Creeping after |                 |
| change/add one feature |        | bus has         |                 |
| what would it be?      |        | stopped"        |                 |
+------------------------+--------+-----------------+-----------------+
|                        | 1      | "Give           |                 |
|                        |        | sound/vibration |                 |
|                        |        | warnings"       |                 |
+------------------------+--------+-----------------+-----------------+
|                        | 1      | "Would like     |                 |
|                        |        | speech "slow    |                 |
|                        |        | down" "your to  |                 |
|                        |        | close""         |                 |
+------------------------+--------+-----------------+-----------------+
|                        | 1      | "To always pick |                 |
|                        |        | up kids in the  |                 |
|                        |        | gutter"         |                 |
+------------------------+--------+-----------------+-----------------+

4.5.3 General Comments

It was generally felt that the FCWS could assist operators in avoiding
forward collisions. Operators indicated that passengers in some seats
could observe the display and that some negative comments had been made
by passengers. One operator felt that there was too much glare from the
DVI, the other five operators felt that there was not too much glare.
Two drivers noted that there is less glare from the DVI than from many
of the other systems on the bus.

In evaluating the DVI it is apparent that the following two main factors
affect the operator's acceptance of the DVI: the false alarm rate of the
system and the degree to which individual operators are either affected
by glare or would prefer not to have a visual display.

While the operators felt that it took a short time to become used to the
system (responses ranged from zero time to a couple of days) they did
recommend that operators needed to be trained with the system prior to
use. The operators did not report any difficulty understanding the top
down mono color illumination method.

Operators' comments varied when asked about the different ranges of
warning activation thresholds that they experienced. Some drivers could
not tell the difference between the different thresholds, so had no
comments (probably due to the short nature of their exposure). Two
drivers said that they wanted the maximum amount of warning time
possible, while two operators said they wanted the minimum number of
warnings.

In these drive-alongs it was observed that all of the operators changed
on occasion their driving behavior to perform a thorough test of the
system. This included speeding up and slowing down behind traffic to
test where the alarms were activated.

It was observed by the researchers that there was a wide range of
driving styles amongst the six operators (some operators were more
aggressive than others). The different driving styles resulted in the
operators receiving differing numbers of warnings. This taken with the
above differences in operator preferences for alarm warning onset
thresholds seems to suggest that operators should have the ability to
change the sensitivity of a FCWS. It was also observed that when
operators could explain why a false alarm occurred (e.g., the system
picked up a fence) they were more satisfied than when they could not
tell what an alarm was for.

4.5.4 Outcome -- DVI refinements

The decision that future iterations should include alternative display
modalities was further confirmed. It was also further confirmed that
operators should be allowed the ability to fully shut off one mode.
Alternative diffuser covers for the display will be further investigated
to see if glare from the DVI can be further reduced. A decision was made
to allow the operators to adjust the sensitivity level of when warnings
come on and to monitor what their preferences are.

4.6 Ongoing operator review

4.6.1 Goal of the Study

To obtain operator feedback after operators have some "in service"
experience with the prototype FCWS and the DVI.

4.6.2 Method

Due to changes in bus assignment two new operators were assigned to the
bus in March, 2002. As none of the operators who were available to meet
from the previous test drive study had been driving the bus in normal
service we were unable to do a follow-up assessment of their opinions at
this time. The two operators were meet by a researcher on the bus with
the prototype system after they had been driving with the system for
approximately two weeks. Both operators are very experienced, one with
18.5 and the other with 20 years. Both operators had driven with the
system for a little over two weeks. The operators were both driving bus
600, which has the original larger DVI. One operator had been given only
a brief description of the system prior to driving, the other had not
been given any training prior to using the system for the two week
period. While this situation was not ideal it did allow us to get a
better understanding of what would happen if deployment occurred without
training. In this session the operators were given an explanation of the
FCWS asked questions and completed a questionnaire. In addition a
limited amount of driving was done in the SamTrans maintenance yard to
try out some different diffuser covers in attempt to reduce the glare
from the DVI.

4.6.3 Feedback

It should be noted that as this feedback is only from two operators it
should be considered preliminary at best, the intention is to gather
further feedback both from these two operators and additional operators
as time goes forward.

Operators generally felt that they would need a few months of driving
before they could fully evaluate the system for issues such as
annoyance. One operator reported "tuning out" the "orange warnings" when
they went off "too often". The operator was not able to define what
period of time was too often.

One operator felt that it would take 2-3 weeks to become comfortable
with the system. One driver reported that the system had been helpful in
busy downtown traffic (at 6pm) and that it had helped make some driving
decisions. **Neither operator reported any situations where the system
was distracting or led them to make an inappropriate maneuver or error
in judgment.** Both operators were interviewed together and filled out
the surveys separately. One operator wanted sound and the other operator
did not. Both operators had driven the system in day and night
conditions. One operator did report that passengers had asked "what's
with the lights", but said that avoiding passenger comments about
anything new is near impossible.

Both operators said that they did not have a problem with glare from the
DVI. The operators also agreed that out of the alternative diffuser
covers tried they preferred the original one.

Operators were asked to rate the DVI on the scale as is shown below:

Table 4 Operator ratings sheet of the visual DVI

+----------------------------+-----------+-----------------------------+
| Question                   | Mean      | Rating Scale Used           |
|                            | Rating    |                             |
+----------------------------+-----------+-----------------------------+
| > How easy is the system   | 5         | (not easy) 1 2 3 4 5 (very  |
| > to use overall?          |           | easy)                       |
+----------------------------+-----------+-----------------------------+
| > How much do you like the | 4.5       | (not at all) 1 2 3 4 5 (a   |
| > system overall?          |           | lot)                        |
+----------------------------+-----------+-----------------------------+
| > How well do you think    | 4.5       | (not at all) 1 2 3 4 5 (a   |
| > the warnings conveyed a  |           | lot)                        |
| > sense of urgency?        |           |                             |
+----------------------------+-----------+-----------------------------+
| > If you had more time     | 5         | (no) 1 2 3 4 5 (yes)        |
| > with the system, would   |           |                             |
| > you like it more?        |           |                             |
+----------------------------+-----------+-----------------------------+
| > Do you think that they   | 5         | (not at all) 1 2 3 4 5      |
| > system is beneficial in  |           | (extremely)                 |
| > terms of increasing your |           |                             |
| > safety?                  |           |                             |
+----------------------------+-----------+-----------------------------+
| > How annoying was the     | 1         | (not at all) 1 2 3 4 5      |
| > system?                  |           | (extremely)                 |
+----------------------------+-----------+-----------------------------+
| > How distracting was the  | 1         | (not at all) 1 2 3 4 5      |
| > system?                  |           | (extremely)                 |
+----------------------------+-----------+-----------------------------+

4.6.4 Outcome -- DVI Refinements

A decision was made not to change the diffuser covers at present, but to
investigate other ways to decrease the brightness of the display.

Arrangements were made to develop a laminated "cheat sheet" that would
explain the FCWS that could be left on the bus. Arrangements are being
put in place to provide training to a larger number of SamTrans
operators.

4.7 Future Work

4.7.1 Operator Acceptance

Ongoing research will be conducted on long term operator acceptance of
the current visual DVI interface, this will involve further meetings and
drive-alongs. Research will be conducted to further refine optimal
levels of false positive alarms. Visual lab studies are planned to
determine optimum timings for the sequencing of colors used in the
display. Operator feedback will also be collected to compare the larger
DVI on the first bus and the smaller DVI on the second bus. Efforts will
also be made to further reduce the level of glare and the amount of
passenger observation from the visual DVI.

4.7.2 Operator Driving Performance

Analysis of operator driving performance data will be performed to
determine if the FCWS changes operators driving in any way. Where
possible driver performance data will be compared prior to the
introduction of the FCWS and after the introduction of the FCWS.
Comparisons will also be conducted between performance with the larger
DVI on the first bus and the smaller DVI on the second bus to see if
they elicit any different driving behaviors.

4.7.3 Multimodal Displays

Alternative display modalities will be further investigated in future
research this will include determining the benefit of implementing
redundancy coding with some form of \"only one modality can be off\"
logic. This approach appears to be a simple, yet effective method of
resolving the daytime/nighttime paradox.

4.7.4 False Alarms / Display Annoyance

A false alarm is a warning issued when there is no threat to the subject
bus at all. A nuisance alarm is a warning given in the case that a
collision is correctly forecasted, but the bus operator does not
consider it to be a true potential threat for the bus \[8 & 9\]. Both
false and nuisance alarms are incorrect warnings (false positives).
While this assessment was intended to address the DVI it is difficult to
parse out what operators find annoying about the display from annoyance
at the false and nuisance alarm rate. Put another way, even the best
display will quickly become annoying if a majority of the alarms are
false or thought not to be required by the operator.

In addition to the false positive rate of the system \[10\] suggests
that the false alarm rate (false positives) of other devices in the
system must also be considered. This has important implications and
should be revisited when the FCWS is combined with other collision
avoidance systems.

In discussing the acceptable number of false positives a majority of
operators felt that they would need to drive with the system for at
least a couple of months to be able to determine how annoying the system
would be. Previous research has not provided guidelines for determining
acceptable rates \[5\]. A study to determine acceptable levels of false
positive when people are driving their own passenger cars by \[11\]
suggests that individuals show a wide range of annoyance sensitivity.
Lerner \[11\] also suggests that annoyance of false positives rates may
change over time. In the same study Lerner et al \[11\] found that a 4
per hour tone and a one per hour voice false alarm was significantly
more annoying than a 1 per hour, 1 per 4 hours or a 1 per 8 hours tone.
However, it is unclear how this finding could be applied in the transit
bus FCWS environment given the different nature of the vehicle, driver,
task and environment.

A number of the operators commented that they felt that their driving
patterns would probably change over time with the system so that the
number of annoying alarms would probably decrease with time as they
"kept better distances from traffic in front". Such a change in driving
patterns when collision warning systems have been implemented was found
in commercial trucks \[12\] and in a separate field review \[13\] of
collision warning systems for heavy trucks it was revealed that out of
171 drivers 80 percent reported changing their way of driving.
Observation of the operators while testing the system suggested that
they quickly learnt points at which they would receive a warning and
then changed their driving to keep from getting an alarm. This was
particularly true on the freeway, possibly because fewer false positives
occurred on the freeway than on local streets. Given the different
driving styles and the differing requests for levels of warning time we
suggest that operators be given the ability to change the sensitivity
threshold of when alarms are activated. This is consistent with previous
researcher's recommendations for CWS \[10\]. This issue will be further
investigated in the next phase of this project.

Another factor that became apparent was that false positives were more
tolerable if the operators could determine what their cause was. For
example, when the system picked up a fence post this appeared to be more
tolerable than when the operators could not determine what the system
was detecting. It would be interesting to know how this affects
long-term use of the system. It would be useful to know if operators
adapt by tuning out all alarms or if they ignore alarms that occur in
situations that produce the largest numbers of false alarms. This does
suggest the need for all operators to be trained on the system so that
they can fully understand what situations are likely to cause false
alarms.

It was also confirmed at this point that operators were less concerned
about the level of false positives if they occurred in the orange
warning condition, as the number of false positives increased in the red
warning condition operators were more frustrated. One operator reported
that they "tuned out" the orange warnings. This is also consistent with
previous human factors recommendations that providing a graded warning
decreases the tradeoff between giving as few false positives as possible
with providing the maximum time for the operator to react \[10\].

4.8 Conclusions

At this point it appears that operator acceptance of the visual DVI and
the FCWS as a whole is very high. Operators have indicated that they
feel that the system could potentially increase their safety.

It is clear going forward that there is a need to determine what effect
(if any) the DVI and the FCWS have on longer term operator performance.
It will be particularly of interest to know how the operators use the
system, preliminary feedback suggests that there is some tuning out of
the orange "advisory" alerts. It will be necessary to determine what
long term effect this will have on the viability of the system. Feedback
from operators emphasizes that for operator acceptance the following
three elements are important:

-   Need to reduce/minimize the false positive rate,

-   Need to provide the option of alternative display modalities and
    that operators must have the ability to switch modalities

-   Need to allow the operator to adjust the sensitivity of alarm
    activation thresholds

-   Need to provide training to operators prior to their using the
    system

These studies (though somewhat preliminary) suggest that the iterative
design process meet its objective of developing a DVI that supports the
operator primary driving task and has a high user acceptance rating.

References

1.  Reinach, S., & Everson, J. (2000). Development of a Preliminary
    Driver Vehicle Interface for a Transit Bus Longitudinal and Lateral
    Collision Avoidance System (Contract No.:DTRS57-99-C-00083).
    Washington, DC: Federal Transit Administration.

2.  Reinach, S., & Everson, J. (2001). The Preliminary Development of a
    Driver-Vehicle Interface for a transit Bus Collision Avoidance
    System. Intelligent Transportation Society of America. Eleventh
    Annual Meeting and Exposition.

3.  Delphi-Delco Electronic Systems, Final Report -- Automotive
    Collision Avoidance System (ACAS) Program (DOT HS 809 080).
    Washington, DC: National Highway Traffic Safety Administration,
    2000.

4.   Seller, P., Song, B., & Hedrick, K. (1998). Development of a
    Collision Avoidance System. Automotive Engineering International.
    109, 24-28

5.  Hancock, P., Parasurman, R & Byrne, E. "Driver-Centered Issues in
    Advanced Automation for Motor Vehicles" in Parasurman, R &
    Mouloua, M. (Eds). Automation and Human Performance: Theory and
    Applications. (pp337-364). Mahwah, NJ: Lawrence Erlbaum Associates,
    1996.

6.  <http://www.kwmuth.com/>

7.  Steinfeld, A., Tan, H.-S., & Bougler, B. (2000). Naturalistic
    findings for assisted snowplow operations. In Proceedings of the
    Human Factors and Ergonomics Society 45th Annual Meeting. Santa
    Monica, CA: Human Factors and Ergonomics Society.

8.  Hirst S., Graham R. The format and presentation of collision
    warnings, cha.11 in Ergonomics and Safety of Intelligent Driver
    Interfaces, edited by Noy Y., 1997.

9.  Burgett, A.L. DOT's approach to ITS safety evaluation, Proceedings
    of ITS America Workshop on ITS Safety Evaluation, May 1995.

10. Comsis Corporation, Preliminary Human Factors Guidelines for Crash
    Avoidance Warning Devices. NHTSA Project No. DTNH22-91-C-07004.

11. Lerner, N.D., Dekker, D. K., Steinberg, G.V., and Huey, R.W.
    Inappropriate Alarm Rates and Driver Annoyance. (DOT HS 808 533).
    Washington, DC: National Highway Traffic Safety Administration,
    1996.

12. Woll, J. (editor), radar-based adaptive cruise control for trucks,
    1998

13. Fukuhara, H., & Kunihiko, K. Essential issues involved in
    radar-based collision warning/avoidance system. Proceedings of IVHS
    America, 1994.

# Section Three  {#section-three .SECTION}

Development of Preliminary Specifications

5 DEVELOPMENT OF PRELIMINARY SPECIFICATIONS

A number of parties have studied the basis of frontal collision
warning/avoidance systems. Eaton VORAD™ developed and commercialized the
EVT- series automotive collision warning systems. DELCO and GM, through
the Defense Advanced Research Project Agency (DARPA) under the
administration of National Highway Traffic Safety Administration
(NHTSA), have been working on the Automotive Collision Avoidance Systems
(ACAS). DENSO and IBEO developed laser scanners for collision
warning/avoidance applications. NHTSA also sponsored a number of
projects under the ITS Crash Avoidance Research Program to develop the
requirements, specifications and relevant techniques for read-end
collision warning/avoidance systems. Publications \[14--18\] and reports
(refs of Burgett \[14\]) discuss collision warning system requirements.

Although the specifications for collision warning radars can be found in
the literature, they may not be suitable for transit bus applications
due to the different application environments, host vehicles and driver
populations. Each of these elements is considered in further detail
below.

\(A\) Application environment differences

Most of the commercial collision warning systems and sensors were
primarily developed for highway applications. Transit buses usually run
at lower speed in urban streets for public transportation services. The
movement of buses is typically stop-and-go. The traffic environment in
urban streets is more complex than that of freeways and highways. Along
bus routes, more objects, such as trees, poles, traffic signs, parked
cars, pedestrians, bicycles, motorcycles, and other vehicles, may be
encountered. The stationary objects in urban streets, e.g. the parked
cars, cannot be simply discarded, because it is possible that the bus is
on a collision course with them.

\(B\) Host vehicle differences

Most of the commercial collision warning systems and sensors were
designed for passenger cars and freight trucks. Transit buses are
designed with lower maneuverability in comparison with cars and trucks
to ensure reliability and safety. The acceleration/deceleration,
steering sensitivity and capability are restricted to prevent on-board
passenger injuries. It takes more time to maneuver a bus to avoid a
crash.

\(C\) Driver differences

The bus operators are professional drivers. They are well trained. Their
reaction to a critical situation may be more efficient than usual
individual passenger car drivers. But their workload is relatively high
during driving. The drivers need to: operate the bus, collect fares,
respond to passenger requests and dispatching commands, keep up with the
schedule, pull the bus in and out the bus stops and take care of
passengers. If not designed appropriately, a collision warning system on
the bus can distract the driver and increase their workload. Driver
acceptance should be emphasized in transit applications.

The following sections provide supporting documentation on the
performance specifications. It should be noted that this document is
based on the developers' knowledge and understanding about FCWS at this
time. As the project continues into the next phase, additional
specification items may be added.

5.1 Development of technical specifications

5.1.1 Subject Vehicle-Status-Sensing Capability

For a collision warning system mounted on a transit bus, the subject
vehicle is the bus, in other words, the bus is the platform for the
collision warning system. Motion of the subject vehicle obviously will
influence the performance of the collision warning system. The motion of
the subject vehicle can be characterized by longitudinal and lateral
kinematical states. The longitudinal states can be represented by speed
and acceleration. The lateral states can be described by lateral speed,
yaw rate, or front wheel angle. Given the wheelbase of the bus, if the
longitudinal speed (one of the longitudinal states) is known, these
three quantities are equivalent to each other. We choose front wheel
angle to represent the lateral states.

\(A\) Speed

The maximum bus speed is restricted. The Gillig bus design specification
has a maximum speed of 64mph (28.5m/s). In the data that PATH collected,
the maximum recorded bus speed is 31.5m/s (70.8mph), this occurred when
the bus was moving on a downhill highway. The maximum bus speed that the
system can measure is specified to be at least **33.3m/s** (75mph), this
should ensure that the FCWS will cover all maximum possible bus speeds.

When a bus is stopped the bus speed is zero. The minimum bus speed that
the system can measure is specified to be no greater than 0.5m/s (1mph).
The reason that the minimum speed is not specified as zero but 0.5m/s is
that when the bus speed is below this minimum value but greater than
zero, the bus is creeping. If the creeping continues, a creeping warning
should be issued, regardless of whether there is an obstacle in a
collision course with the bus. It is optimal though not a requirement
that the FCWS functions if a creeping warning is issued. The EVT-300
Eaton VORAD™ collision warning system has host vehicle speed coverage of
0.5-120 mph (0.8-190 km/hr, or 0.2\~52.8m/s).

\(B\) Acceleration

The accelerating performance of the bus is restricted. The Gillig bus
takes at least 2.05sec to speed up to 10mph from rest, 6.33sec to 20mph,
12.87sec to 30mph, 23.0sec to 40mph, 38.2sec to 50mph, 60.37sec to
60mph; the peak deceleration (slowing down) of Gillig bus is
23.8ft/sec^2^ (7.25m/s^2^), average deceleration usually is between
6.4-9ft/sec^2^ (1.95-2.74m/s^2^) (J. Moon of Gillig). Average
acceleration of Gillig bus in the first two seconds is 2.17m/s^2^. In
the data that PATH collected, the maximum bus acceleration recorded is
0.523g (1g=9.8m/s^2^); the maximum bus deceleration is 0.692g. The
maximum acceleration/deceleration that the system can measure is
specified be at least **0.55g/-0.75g** (negative for deceleration). The
minimum bus acceleration/deceleration that the system can measure should
be no greater than ±0.05g. It is better if all possible accelerations
/decelerations are covered.

\(C\) Wheel angle

In the data that PATH collected, the maximum front wheel angle recorded
is 45.5 degrees to the right, 50 degrees to the left. The maximum front
wheel angle that the system can measure is specified to be at least 50
degrees for both right and left.

Note that a real FCWS doesn't necessarily have to measure these states
to fulfill the warning function. However, the system must be functioning
when the bus states are within these specified ranges.

5.1.2 Object-Sensing Capability

5.1.2.1 Spatial coverage and resolution

As is shown in the specifications the spatial coverage of transit FCWS
is illustrated in Fig. 71. The coverage proposed herein is the minimum
system requirement for object detection. The system may cover larger
areas.

  -----------------------------------------------------------------------
  ![](media/image6.wmf)

  Fig. 2 Spatial coverage illustration
  -----------------------------------------------------------------------

Based on the Stopping Distance Algorithm (SDA) and Closing Rate
Algorithm (CRA), Kenue \[18\] conducted Monte-Carlo simulation to assess
how the maximum range and azimuth angle selection affects the accident
detection rate of a FCWS. The decelerations of both the lead vehicle and
the host vehicle, and total delay time, including the driver reaction,
sensor processing, and brake reaction time were taken into account in
the simulation. The conclusion is that "further increasing the range
beyond 300 feet does not increase the potential accident warning rate
and that multi-beam sensors have a higher probability of accident
warning as the number of beams increase." (p 497). Where micro-wave
sensors are used multiple beams cover adjacent lanes. The recommended
azimuth angle coverage at 250-275 feet is 8-9 degrees, as this can cover
adjacent lanes on a curved road.

The EVT-300 Eaton VORAD™ collision warning system has a range coverage
of 0.9-110 meters (typical); azimuth angle coverage of 12 degrees (6
degrees to both the right and the left). The Denso laser scanner covers
up to 160m with 10 degrees to both the right and the left (20 degrees in
total). \[17\] suggests that multiple beam micro-wave sensors should
have a range coverage of 100-150 meters with +/-1m resolution, and 10-14
degrees azimuth Field Of View (FOV).

We specify the maximum range as 100 meters. This can be calculated from
the extreme situation given bus speed 28 m/s, deceleration 5m/s^2^,
facing a static object, driver's typical reaction time .75s. The
distance that is needed to stop the bus is
28\*28/5/2+28\*0.75=28\*3.55=99.4 meters. This calculation shows 100m
maximum range shall cover most of the potential accidents.

We specify the azimuth coverage as 30 degrees with a coverage range of
12 meters at the maximum angle. The wider angle is for early detecting
cut-in vehicles. Review of the accident data and field data suggests
that cut-ins happens more often in front of a bus and that passenger car
drivers usually pass a bus rather than follow it. The 30 degree coverage
assures that the system can detect the front half of a passenger can in
the next lane when the car's back is in line with the bus front bumper.
It should be noted that the 30 degrees is not necessarily the nominal
azimuth angle coverage of a specific sensor, because the range
requirement at the maximum angle, that is 6\*2=12 meters, is much
shorter than that for the forward direction. For a microwave radar, the
nominal azimuth FOV is usually defined as the 3dB beam width. The
lateral coverage is specified as 6 meters to cover one and half lanes.

5.1.2.2 Timing and update rate

\(A\) Delay

See 5.3.1.2 (A) for delay specifications explanation.

\(B\) Update Rate

The sensor data update rate is specified to be at least 10 Hz. This
update rate is required because the tracking algorithm shall associate
consecutive measurements to refine the object state estimations. This
update rate assures that the association area will not exceed 3 meters,
which is approximately half the size of a passenger car.

5.1.3 Warning system

5.1.3.1 Power supply

\(A\) Voltage

The power supply should be compatible with the bus battery, i.e. 12V or
24V DC as this provides the most convenient power supply interface. High
voltage is prohibited on transit buses because of safety considerations.

\(B\) Power consumption

The Gillig buses can provide 300+ watts power capacity for extra
electronic equipments. The total warning system power consumption should
be no greater than 100W to reserve some capacity for other systems, such
as side- and rear- collision warning systems. The Eaton VORAD™ EVT-300
power requirement is 20W.

5.1.3.2 Processing capability

\(A\) Delay

The processing delay from system input to output should be no longer
than 0.5 s (this includes the maximum 0.3s sensor delay). The sensor
delay is needed to collect data to estimate speed from position
measurements or acceleration from velocity measurements. The extra 0.2s
system delay is needed to assess the situation. Longer delay may help to
improve the accuracy of estimation and assessment; however it is
unacceptable because the human driver will realize the system delay. Too
much system delay will negatively affect the system performance as
warnings may either be displayed too late for the operator to respond to
them or they may arrive after the operator is responding to the
potential threat which will either distract the operator (which could
have hazardous consequences) and/or decrease operator trust in the
system. Any decrement in operator trust may lead the operator to ignore
the system. Previous research on the development of a lane change,
merging and backing collision avoidance system \[25\] found that drivers
did not notice a delay of .5 seconds.

\(B\) Update rate

The system processing batch rate should be at least 2 Hz. More frequent
update of warning information may improve the timeliness of the warning,
but warnings that are shorter than half a second will be annoying. Once
a warning is detected, the signal sent to the DVI is suggested to keep
on for about half a second.

5.2 Development of Performance Specifications

5.2.1 Object Presence Detection Performance

The object presence detection performance is a matter of output
Signal-to-Noise Ratio (SNR), i.e. how well the system can suppress noise
and clutters. It is convenient to use probability of detection (P~d~,
true object detection) and probability of false alarm (P~fa~, false
object detection) to describe detector performance. The relationship
between SNR and (P~d~, P~fa~) can be found in the *Radar Handbook*
\[19\]. False alarm time is defined as the average time between false
alarms. False alarm time is a more practically useful concept, which is
equivalent to P~fa~.

Colgin \[20\] reported a mathematic model for simulating FMCW radar
performance at 76.5GHz working frequency. The model calculates radar
performance in distributed background clutter, along with atmospheric
attenuation, due to air, rain, snow or fog. Multi-path effect and target
fluctuations are taken into account. The model was calibrated assuming
that a 1m^2^ non-fluctuating target at 100m produces a SNR of 24.1dB at
the peak of the beam and the peak of an FFT filter. The report shows the
Signal-to-Clutter plus Noise Ratios (SCR) in: ground only clutter,
ground plus rain clutter, ground plus snow clutter and ground plus fog
clutter, at 24.1dB, 21.2dB, 22.8dB are 24.0dB respectively. The *Radar
Handbook* reports that for non-fluctuating targets, this level of SNR
can bring P~d~ to almost 100% and lower than 10^-12^ P~fa~, for the
Swerling case 1 fluctuating targets, this level of SNR can bring to 90%
P~d~ and 10^-6^\~10^-12^ P~fa~.

We specified the average P~d~ and P~fa~ in all possible atmospheric
conditions, with 99% P~d~ allowing one false alarm in every two hours.
Atmospheric condition is a critical factor that affects the detector
performance. In rainy, foggy or snowy days, P~d~ may be a little bit
lower than the specification, or false alarm time may be slightly
shorter than the specification. The specification is based on the
assumption that there are 10% of rainy days, 10% of foggy days, 10% of
snowy days and 70% of clear days. To avoid confusion the terms true
object detection and false object detection are used in the
specification.

5.2.2 Collision Detection Performance

A false alarm is a warning issued when there is no threat to the subject
bus at all. A nuisance alarm is a warning given in the case that a
collision is correctly forecasted, but the bus operator does not
consider it to be a true potential threat for the bus (see Burgett's
interpretation \[9\] and \[10\]). Both false and nuisance alarms are
incorrect warnings (false positives).

Traffic safety facts show that nationally 1.8 million rear-end crashes
happen annually, while the same drivers brake perhaps 10 trillion times
to prevent a crash \[14\]. This indicates that the probability of a real
crash is very low, approximately 10^-7^. The probability of a false
object detection is very low as well, see the previous section for false
object detection probability. It is therefore evident that most of the
warnings will be nuisance alarms.

Prior Human Factors research reports that drivers try to match their
response rates to the reliability of the warnings (\[23\] and refs). It
will be distracting and disturbing to the driver if warnings are issued
too frequently, as most of the warnings are nuisance alarms which bring
little information to the driver. But if the system never emits a
warning, the driver may be startled by first warning and not respond
appropriately \[24\]. This implies that the appropriate warning rate
must be within a range, and the warning rate is driver-dependent.

In the development work for this project operators felt that they would
need to drive with the system for at least a couple of months to be able
to determine appropriate levels of nuisance alarms. Previous research
has not provided guidelines for determining acceptable rates \[26\]. A
study to determine acceptable levels of false positive when people are
driving their own passenger cars by Lerner et al \[26\] suggests that
individuals show a wide range of annoyance sensitivity. Lerner et al
also suggests that annoyance of false positives rates may change over
time. In the same study \[26\] found that a 4 per hour tone and a one
per hour voice false alarm was significantly more annoying than a 1 per
hour, 1 per 4 hours or a 1 per 8 hours tone. However, it is unclear how
this finding could be applied in the transit bus FCWS environment given
the different nature of the vehicle, task, driver and environment. In
the absence of any specific guidelines we suggest setting a preliminary
warning rate range of within 1 to 4 warnings per hour. This rate will be
updated as further studies are conducted in this area.

References

14. Burgett, A.L.; Miller, R.J. A new paradigm for rear-end crash
    prevention drving performance. 2001-01-0463

15. Woll, J.D. Monopulse Doppler radar for vehicle applications. M+RF97
    Microwave and Communications Technologies Conference Proceedings,
    Swanley, UK: Nexus Information Technology, 1997. p.234-8.

16. Morenc, N.P.; Lajiness, G.G. 76 GHz collision warning transceiver
    component requirements and current status, Intelligent
    Transportation System, 1997. ITSC \'97, IEEE Conference on, 1997,
    Page(s): 439 --445.

17. Dixit, R.; Rafaelli, L. (Edited by: Koepf, G.A.) Radar requirements
    and architecture trades for automotive applications. 1997 IEEE MTT-S
    International Microwave Symposium Digest, New York, NY, USA:
    IEEE, 1997. p.1253-6 vol.3.

18. Kenue, S.K. Selection of range and azimuth angle parameters for a
    forward looking collision warning radar sensor. Proceedings of the
    Intelligent Vehicles \'95. Symposium, New York, NY, USA: IEEE, 1995.
    p.494-9.

19. Skolnik, M.I. (ed) Radar Handbook, 2nd ed, McGraw-Hill, Inc. 1990.

20. Colgin, R.C. FMCW radar math model report for radar sensor
    simulations, Dec. 1999, GM Confidential.

21. Burgett, A.L. DOT's approach to ITS safety evaluation, Proceedings
    of ITS America Workshop on ITS Safety Evaluation, May 1995.

22. Hirst S., Graham R. The format and presentation of collision
    warnings, cha.11 in Ergonomics and Safety of Intelligent Driver
    Interfaces, edited by Noy Y., 1997.

23.  Lehto, M.R., Papastavrou, J.D., Ranney T.A., Simmons L.A. An
    experimental comparison of conservative versus optimal collision
    avoidance warning system thresholds, Safety Science 36, 185-209,
    2000.

24.  Hancock, P.A., Parasuraman R., Byrne E.A. Driver-centered issues in
    advanced automation for motor vehicles, chapter 16 in Automation and
    Human Performance: Theory and Applications, edited by Parasuraman R.
    and Mouloua M., 1996.

25.  Eberhard, C., Moffa, P., Young, S., & Allen, R. (1995). Development
    of Performance Specifications for Collision Avoidance Systems for
    Lane Change, Merging and Backing -- Interim Report. DOT HS 808 430.

26. Lerner, N.D., Dekker, D. K., Steinberg, G.V., and Huey, R.W.
    Inappropriate Alarm Rates and Driver Annoyance. (DOT HS 808 533).
    Washington, DC: National Highway Traffic Safety Administration,
    1996.

#########  {#section-2 .Reference .unnumbered}

6 Transit Bus Frontal Collision-Warning Systems: Preliminary Performance
Specifications

6.1 Interface Requirements

This performance specification represents the research conducted under
the Transit Bus Frontal Collision Warning System project sponsored by
the Federal Transit Administration (FTA) in 1999. The goal of this
project is to develop performance specifications for transit bus frontal
collision warning systems (FCWS).

This work was undertaken in conjunction with the FTA by California PATH
of UC Berkeley, in partnership with San Mateo County Transit District
(SamTrans) in California, California State Department of Transportation
(Caltrans) and bus manufacturer Gillig Corporation (Gillig).

PATH began this project by conducting the following tasks:

1.  A literature review to determine the impact of frontal collisions on
    the transportation industry and to determine if any similar systems
    are currently deployed

2.  A review of transit bus accident statistics in the San Francisco Bay
    Area (California)

3.  Development of a kinematical model showing movements of the bus and
    surrounding vehicles prior to a collision

4.  The development and implementation of a data collection system
    including sensors, cameras, and data recording devices on a SamTrans
    bus

5.  Ongoing industry discussion with San Francisco Bay Area transit
    agency advisory committee members

6.  Ongoing Bus Operator meetings with SamTrans employees

In conjunction with the above tasks, PATH developed a prototype FCWS on
a Gillig manufactured SamTrans owned bus to verify the specifications
for the FCWS (see the final project report for further details). It is
important to note that as these specifications are based in part on
information collected from the PATH developed prototype used by SamTrans
employees on regular normal services in the SamTrans service area, it
has not been validated in any other area, on any other bus, or with
operators outside of SamTrans employment.

Some items in this document are expressed in terms of sensing
capabilities, these are not requirements for specific sensors, they
should be considered as the working condition requirements for a FCWS.
Other items (for example, the collision detection and driver vehicle
interface characteristics) are given as design considerations rather
than specifications due to the complex nature of the issues involved and
the fact that there may not be one best way to specify for future
developers or that the issue requires further verification in a longer
term study with a working system. It is envisaged that in these cases
the function of the system should be recommended and that developers
should meet those functional requirements.

This document represents the developers' current understanding of FCWS
requirements. It might not be a complete set of requirements for FCWS.
As the development efforts continue, additional specification items may
be added.

6.1.1 Definitions

6.1.1.1 System functions

The functional goals of the FCWS are to address imminent potential
crashes, by providing a warning to the operator in unsafe situations and
to provide environmental guidance for smoother maneuvering. The primary
goal of the frontal collision warning system is to predict imminent
potential crashes, or collisions with objects. To achieve these goals
the collision warning system must have the sensing capability to gather
information from both the subject vehicle and the surrounding
environment (subject and object sensing). The system then must fulfill
the following five basic signal and data processing functions: object
detection, object status estimation, collision detection, collision
severity assessment, and generation of warning signals.

\(a\) Subject and object sensing

A FCWS may need to: assess the bus status, detect operator actions,
obtain environment information, and measure object status. Sensors will
be used to provide the necessary inputs to the system. The system
sensing capability can be divided into two categories: subject vehicle
status and object status sensing.

\(b\) Subject vehicle status sensing

Subject vehicle status sensing refers to the acquisition of information
on operator operations and the current kinematical states of the bus.
Examples of subject vehicle status sensors are: speedometers,
accelerometers, brake pressure sensors, steering angle sensors, and GPS
receivers.

\(c\) Object status sensing

Object sensing refers to the acquisition of information from the
environment (for example, road curvature), the presence of other objects
(for example, vehicles and pedestrians) and the current kinematical
states of the objects. Examples of sensors for object status sensing are
microwave radars, laser radars, imaging sensors and ultrasonic sensors.

6.1.1.2 Signal and data processing

\(a\) Object detection

The function of object detection is to tell if there is an object within
the monitoring coverage of the collision warning system.

\(b\) Object status estimation

The function of object status estimation is to determine the kinematical
states of an object; these states may include such information as
spatial position, velocity and acceleration of an object.

\(c\) Collision detection

The function of collision detection is to determine if the bus and an
object will collide in a certain period of time.

\(d\) Collision severity assessment

The function of collision severity assessment is to determine the
potential severity of a collision by assessing such factors as the
probability of a collision, time to the potential collision and the
likely damage of a collision.

\(e\) Generation of warning signal

This function generates the warning signals that are displayed to the
operator.

**Note:** Some radars and lidars may already implement functions (a) and
(b) as preprocessing functions.

6.1.2 Driver-Vehicle Interface (DVI)

The DVI reports the outputs of the FCWS to the operator for appropriate
corrective action. These signals are presented via displays whose
modalities may include any of the following: visual, auditory, tactile
(vibration), and/or haptic (force). Displays may use a combination of
binary and graded warnings.

\(a\) Binary warnings

Binary warnings are those which are either on or off. They may include a
ramp-up in amplitude or other characteristics; however, these ramp-ups
are independent of the scenario (e.g., the volume increases quickly over
0.5 seconds every time the alarm sounds).

\(b\) Graded warnings

Graded warnings indicate multiple levels of warning and may be
continuous or discrete in nature. The level of warning is tied to the
measure of warning necessity.

6.2 Technical Specifications

6.2.1 Transit Bus Status Sensing Capability

The following items specify the sensing capability requirements. The
transit bus interface should include signals for speed, steering angle,
and provide system power. All system interfaces should be non-invasive
to prevent interference with transit bus operation. The FCWS should be
functioning in the following given conditions.

6.2.1.1 Speed

The maximum bus speed that the system can measure should be at least
33.3m/s (75mph). The minimum bus speed that the system can measure
should be no greater than 0.5m/s (1mph). It is more preferable if all
possible speeds are covered. The scalar speed sb of the bus should be
known to within 5 %.

6.2.1.2 Acceleration

The maximum subject vehicle acceleration/deceleration that the system
can measure should be at least 0.55g/-0.75g (1g = 9.8m/s^2^, negative
for deceleration). The minimum bus acceleration that the system can
measure should be no greater than ±0.05g. It is more preferable if all
possible accelerations/decelerations are covered.

6.2.1.3 Wheel angle

The maximum front wheel angle that the system can measure should be at
least 50 degrees to both right and left. It is more preferable if all
possible front wheel angles are covered. The Yaw-rate
${\overset{˙}{\theta}}_{b}$of the bus should be known to within +/- 1
deg/sec.

6.2.2 Object-Sensing Capability

6.2.2.1 Spatial coverage and resolution

Spatial coverage is illustrated in Fig. 72. The coverage proposed herein
is the minimum system requirement for object detection. The system may
cover larger areas.

  -----------------------------------------------------------------------
  ![](media/image7.wmf)

  Fig. 3 Spatial coverage illustration
  -----------------------------------------------------------------------

6.2.2.2 Range

The farthest detectable range in the same lane should be at least 100m
(330ft). The closest detectable range in same lane should be no greater
than 3m (10ft). The resolution should be finer than 1m (3.3ft).

6.2.2.3 Range-rate

The maximum detectable range-rate should be at least 20m/s (45mph,
separating). The minimum detectable range-rate should be no greater than
-44m/s (--100mph, approaching). It is more preferable if all possible
range-rates are covered.

6.2.2.4 Azimuth or lateral position

The maximum detectable side-looking angle from the front bus corners
should be at least 30 degrees. The maximum lateral position should be at
least 6m (20ft).

6.2.2.5 Elevation field of view

The field of view in the forward looking direction is 4DEG.

6.2.2.6 Timing and update rate

\(a\) Delay

The sensing delay from sensor input to output should be shorter than 0.1
s.

\(b\) Update rate

The sensor data update rate should be at least 10 Hz.

6.2.2.7 Sensor alignment requirements

\(a\) Spatial alignment

Most sensors for object sensing measure the environment in their own
coordinate frames. These measurements need be transformed to a common
system coordinate frame which is fixed with the subject bus. Calibration
may be needed to determine the spatial relationship between the sensor
coordinate frames and the common system coordinate frame. It should be
easy to do field calibration of these systems.

\(b\) Temporal alignment

Sensors and computers may have their own timing clocks which are running
independently. Different sensors may have different delays or update
rates. From the system point of view, sensor measurements should be
aligned in time to ensure that the data collected simultaneously from
all sensors is describing the same scenario at the same instant.

\(c\) Metrological alignment

All measurements should be converted into the same metrological system.

6.2.2.8 Sensor protrusion

All sensors shall not protrude more than 6 inches outside the envelope
unless a sufficient guard is put into place.

6.2.2.9 Sensor cleaning

All sensors shall be operational with only one daily cleaning. The
cleaning procedure should be provided in the systems operational
procedure.

6.2.3 ICWS Power Requirements

6.2.3.1 Power supply

\(a\) Voltage

The power supply should be compatible with the bus battery, i.e. 12V or
24V DC.

\(b\) Power consumption

The total ICWS power consumption should be no greater than 350W.

6.2.4 ICWS Processing Capability

6.2.4.1 Latency

The processing delay from system input to output should be no longer
than 0.3 seconds (this includes the maximum 0.1 second sensor delay).
The ICWS shall compensate for this computational latency in the
probability calculations and generate the safety level at the correct
time

6.2.4.1 Update rate

The system processing batch rate should be at least 2 Hz.

6.3 Performance specifications

6.3.1 Object Presence Detection Performance

6.3.1.1 Probability of true object detection

The probability of true detection of a passenger-car-like object should
be greater than 99.9%.

6.3.1.2 False object detection time

False object detection is defined as a target detected without any
substantial object presence. The mean time between two consecutive false
object detections should be at least 2 hours. It should be noted that a
false object detection does not necessarily lead to a false collision
detection, because a warning is issued only if the system determines
that the falsely detected object is on a collision course with the bus.

6.3.2 Collision Detection Performance

A false alarm is a warning issued when there is no threat to the subject
bus at all. A nuisance alarm is a warning given in the case that a
collision is correctly forecasted, but the bus operator does not
consider it to be a true potential threat for the bus. Both false and
nuisance alarms are incorrect warnings (false positives). Given that by
definition what constitutes a nuisance alarms is determined by operators
it can be expected that nuisance alarm rates will be driver-dependent.
Previous human factors research suggests the need to balance the total
number of alarms with the number of false alarms.

6.3.2.1 False positive rate

Previous human factors research suggests that too many false alarms will
result in a loss of operator confidence and trust in a system. This loss
of confidence and trust can lead operators to either ignore the system
or spend valuable time verifying each alarm; both of these options will
decrease the effectiveness of the system. The FCWS shall generate less
than 5% False Positives.

6.3.2.2 Total number of alarms

If the total number of false and nuisance alarms is kept to a minimum
and given that the probability of a real crash is very low, it is likely
operators will not receive any alarms for long periods of time. In this
case when an operator does receive an alarm the alarm may produce a
startled response resulting in a longer response time which will
decrease the effectiveness of the FCWS. It has been suggested that some
false and nuisance alarms will minimize this effect.

This implies that the appropriate warning rate must be within a range,
and the warning rate is driver-dependent, i.e. the optimal warning rate
for different drivers may be different. The acceptable warning rate
issue is still under investigation in the field of human factor. See for
considerations of correct warning performance.

6.3.3 Warning Algorithm Performance

6.3.3.1 Safety levels for FCWS

The FCWS shall generate the appropriate safety level as defined below
based on object type, probability of collision, and time to collision,
as given by the following charts

**Alert --- Potential obstacles exist and may pose a collision hazard.**

**Warn --- Collision is imminent without evasive action.**

6.3.3.2 Warning thresholds

Whatever safety measures are used, warning thresholds which are to be
compared with the safety measures should be able to match with drivers'
normal operational performance. Diversity of driver performance should
be taken into account, thus multiple sensitivity levels may be needed to
provide sensitivity options for drivers.

6.3.3.3 Warning algorithm hysteresis

The FCWS shall provide hysteresis in generating safety levels to prevent
toggling of the DVI Inputs. Safety levels will be output for a minimum
of 0.5 seconds unless overridden by a higher safety level.

6.4 Suggested Design Considerations

6.4.1 Correct Warning Performance

6.4.1.1 Correct warning probability

Under the condition in section 5.2.2, the total detection probability of
correct warnings should be as high as possible, and the warning should
be displayed to the operator as early as possible, so to minimize any
potential damage.

6.4.1.2 Odds of a correct warning

A correct warning occurs when the situation (including the operator)
requires a warning. The specification of odds of a correct warning shall
be determined in the field test. The odds of a correct warning should be
as high as possible. We will investigate this issue further in phase two
of this project.

6.4.2 Operator behavior performance

6.4.2.1 Response time

It will be necessary for a transit bus FCWS to induce a response no
slower than under normal conditions. Even small savings in response time
can be considered beneficial as they will impact on the probability of a
crash. In the event of a crash, small improvements in response time will
reduce the severity as the speed of the bus will likely be lower.

6.4.2.2 Braking behavior

Due to the risk of passenger falls the system should promote earlier
braking rather than harder braking.

6.4.2.3 Swerving behavior

Due to the size and mass of transit buses it is preferred that the
system does not induce excessive, swerving behavior. Swerves that are
executed with complete situational awareness are not as risky, but in
surprise conditions the operator may not be fully aware of objects to
the side of the bus.

6.4.2.4 Passenger considerations

######### A major concern of transit agencies is passenger falls. The system displays (visual, audible, etc.) should not be readily observable by the passengers. This will reduce the risk of fraudulent passenger fall claims and causing unnecessary surprise or concern from passengers. {#a-major-concern-of-transit-agencies-is-passenger-falls.-the-system-displays-visual-audible-etc.-should-not-be-readily-observable-by-the-passengers.-this-will-reduce-the-risk-of-fraudulent-passenger-fall-claims-and-causing-unnecessary-surprise-or-concern-from-passengers. .Reference .unnumbered}

7 Summary

Analysis of accident data collected from selected Bay Area and
California transit agencies indicates that frontal collisions constitute
20-30% in statistics and 30-40% of cost of all transit related
accidents. These collisions typically result in property damage, service
interruptions and personal injuries while contributing to an increase in
traffic congestion. This projects accident analysis, feedback from
transit agency representatives from the Bay Area Transit Advisory
Committee, and driver feedback indicate that an effective collision
warning system could help to reduce the likelihood of accidents and
facilitate smooth driving.

Previous collision warning and collision avoidance systems have focused
exclusively on highway applications for trucks and light-duty passenger
cars. No previous work was found on frontal collision warning systems
for transit buses. The research for this project suggests that there are
two fundamental differences between a transit collision warning system
need and that of a highway truck or light-duty passenger car system. The
first is the operating environment, an urban and suburban operating
environment is dramatically different from those targeted in previous
studies. The different environment presents a considerable challenge
with respect to the presence of a much larger number of objects needing
to be screened for hazards and due to the more complicated traffic
patterns. Secondly as transit bus drivers are professional drivers they
may have different needs from and sensitivities to a collision warning
system. In the process of the developing requirement specifications,
both of these issues were addressed.

The primary goal of this project was to develop the performance
requirement specifications for the frontal collision warning system for
transit buses. To accomplish this goal, the FCWS team has applied System
Engineering Process (SEP) in the requirement analysis process. To
support the primary goal, research was conducted in the areas of data
collection and analysis. In addition the team maintained a driver needs
focus in all phases of the study and verification of requirements
through field-testing. Each of these activities are further described
below.

**Accident Data Analysis:** In order to define the operational
environment and the bus operation scenarios, thorough data collection
and analysis was conducted. In addition to reviewing national accident
statistics, accident records collected by SamTrans and 34 additional
transit agencies were analyzed. The accident data analysis revealed that
bus frontal collisions mostly occur at low velocity on suburban
corridors, local streets and near bus stops, traffic lights, or
intersections. Many incidents involved the bus making contact with a
neighboring vehicle at the front corners at relatively low speeds. In
addition to frontal collisions, passenger falls resulting from emergency
braking also contribute to an increased potential for passenger injuries
and liability.

**Field Data Collection and Analysis** was an essential element of this
project. The accident data provides a knowledge base for determining the
type and frequency of frontal collision accidents. However, because
transit accident data are heavily dependent on the recollection of the
involved operator, most data may not accurately describe the cause and
the time sequence of accidents. In order to further understand the
environment that a CWS will operate in, data acquisition systems were
developed and instrumented on three SamTrans buses. The data acquisition
system collected several types of data, including sensor data such as
detecting the presence and relative motion of obstacles in front of the
bus, vehicle status (i.e., velocity, acceleration and steering angle),
and video data. A data analysis tool was developed to overlay the
sensory data onto the video data to enable us to see what sensors
detect. A second tool is being developed for automating the data
analysis process.

The team was not expecting to acquire actual collisions during the
course of this project, However, the abundant data collected on these
buses provides us with an accurate description of the relative movement
of the buses, the surrounding vehicles and potential crash scenarios. In
the absence of collisions, hazardous conditions that potentially can
lead to accidents have been identified and driver reactions to these
hazardous conditions have been analyzed. The in-depth understanding of
bus operating environment and hazardous conditions helped to establish
scenarios under which accidents may occur and provide a foundation for
the determination of sensor performance, and system specifications.
Currently there are over 200 gigabytes of video and sensory data stored
on a Redundant Array of Inexpensive Disks (RAID). Additional data is
being collected and data will continuously be analyzed in the Phase Two
project.

**A Prototype Frontal Collision Warning System** was also developed. The
hardware platform was based on the data collection system hardware in
order to evaluate the preliminary functional requirements and technical
specifications. A preliminary collision-warning algorithm was
specifically designed for bus operation in an urban environment.
Significant efforts were devoted to deal with problem areas revealed
through the data collection process using the playback tool and the
collected data. The current warning algorithm, which was evolved through
different stages of the project, has much better performance in dealing
with most of false positive patterns.

It has been realized that the probability of a true collision is so
small that suppression of false alarms or nuisance alarms is the central
point for developing a FCWS, particularly for operation in urban
environment. The project team recognized that several signal processing
and sensor fusion techniques such as object recognition and
classification, GPS map utilization, driver status monitoring may all be
helpful for reducing nuisance alarms in the future. Random models may be
better than deterministic models in terms of describing the evolution of
vehicle states. These techniques will be considered in the second phase
of the FCWS.

The **Driver Vehicle Interface (DVI)** is a critical element for
effective communicating the warning information to the driver. Through
iterative studies of the driver needs and desires, a prototype visual
DVI was developed. So far, field tests have shown that operator
acceptance of the visual DVI and the FCWS as a whole is very high.
Operators have indicated that they feel that the system could
potentially increase their safety. The project team has determined that
there is a need to determine what effect (if any) the DVI and the FCWS
have on longer-term operator performance. It is particularly of interest
to know how the operators use the system. Preliminary feedback suggests
that there is some "tuning out" of the amber "advisory" alerts. It is
necessary to determine what long-term effect this will have on the
viability of the system. Feedback from operators emphasizes that the
acceptance of the system relies on the reduction/minimization of the
false-positive rate, options for alternative display modalities, ability
to adjust the sensitivity of the alarm activation thresholds, and
training to operators prior to their using of the system.

The DVI study under this project (though somewhat preliminary) suggests
that the iterative design process meet its objective of developing a DVI
that supports the operator primary driving task and has a high user
acceptance rating. The FCWS team will continuously use this approach to
ensure that the collision warning system can indeed help to reduce both
the frequency and severity of collisions. Topics that need further
examination include warning thresholds for both advanced cues and
critical warnings, alternative modalities, and the impact of transit
specific driving tasks.

As the final product of this project, the **preliminary performance
requirement specifications** for transit FCWS are developed.

Based on the research separately conducted on advanced technologies for
frontal and side collisions, starting late 2002, Caltrans, CMU, PennDOT,
PAT, Samtrans and UC PATH, in partnership with FTA have committed to
conduct further development on an integration of the advanced side
collision warning and frontal collision warning systems into a unified
whole with one transit operator interface. This work will lead to a
unified collision warning system specification of Integrated Collision
Warning System (ICWS) and two prototypes for limited operational
testing. The goals identified by the ICWS team are to (1) develop a
Functional ICWS, (2) create a system acceptable to operators (drivers &
operations), (3) demonstrate a potential for reduction in the severity
and frequency of collisions and (4) prove technical feasibility through
field test of prototype system(s). Under the ICWS project, the FCWS are
being improved and as part of the ICWS performance requirements, the
FCWS performance requirement specifications will be finalized. The ICWS
project is scheduled to be complete by mid 2005.

# Section Eight {#section-eight .SECTION}

# Appendix 

Appendix I: List of 32-CalTIP Members

1.  AMODOR Regional Transit System

2.  City of Arcata & Mad River Transit System

3.  City of Auburn

4.  City of Azusa

5.  Butte County

6.  Central Contra Costa Transit Authority

7.  Culver City

8.  City of Dixon

9.  El Dorado County Transit Authority

10. City of Folsom

11. Golden Empire Transit District

12. Humboldt Transit Authority

13. City of Lincoln

14. Livermore Amador Valley Transit Authority

15. City of Lodi

16. Mendocino Transit Authority

17. Monterey-Salinas Transit

18. Morongo Basin Transit Authority

19. Napa County Transportation Planning Agency

20. Nevada County

21. Placer County Transit

22. Riverside Transit Agency

23. San Luis Obispo Regional Transit Authority

24. Santa Cruz Metropolitan Transit District

25. Siskiyou County

26. South Coast Area Transit

27. South County Area Transit

28. City of Vacaville

29. City of Vallejo Transit

30. Western Contra Costa Transit Authority

31. City of Whittier

32. Yolo County Transportation District

Appendix II: Sample JGAA Cost Report

Div ALL Select Period: As of: Activity Period: Printed: 09/11/2002 Page:
1

07/01/1994 - 09/11/2002 09/11/2002 -

Selected by: Claims With Incurred from: Examiner ID: ALL

DATE OF LOSS -\$999,999,999 thru \$9999999999 Leg/Oth: YES Recovs: NO

Proc Off: ALL ALL CLAIMS IN CLAIM NUMBER ORDER FOR CALENDAR YEARS
1994-2002 Info-Only: YES Late-Rpt: YES

Maint-Only: YES \*HistSumm: N/A

====================================================================================================================================

Claim Sts Carrier Loss Reported Entry Denied Closed Reopen Paid in
\-\-\-\-\-\-\--TOTALS AS OF: 09/11/2002\-\-\-\-\-\--

No No Date Date Date Date Date Date Pay Period Paid Reserve Incurred

====================================================================================================================================

0053740 C 01/09/00 01/14/00 01/18/00 01/31/01

Loss: 63 ON BRD-STOPPING Desc: ABRUPT STOP PAX FELL

Claimant: XXXXXXXXXXXXXXXXXX Bod Inj: 0.00 400.00 0.00 400.00

Totals: 0.00 400.00 0.00 400.00

\-\--CLAIM SUMMARY\-\-- Totals: 0.00 400.00 0.00 400.00

\-\-\-\-\-\-\-\-\-\-\-\-- \-\-\-\-\-\-\-\-\-\-\-\--
\-\-\-\-\-\-\-\-\-\-\-\-- \-\-\-\-\-\-\-\-\-\-\-\--

NET: 400.00

0053750 C 01/13/00 01/17/00 02/01/00 03/15/00

Loss: 8 TRN LFT-OTH LFT Desc: UNSAFE LANE CHANGE VEHICLE COLLI

Claimant: XXXXXXXXXXXXX Totals: 0.00 0.00 0.00 0.00

\-\--CLAIM SUMMARY\-\-- Totals: 0.00 0.00 0.00 0.00

\-\-\-\-\-\-\-\-\-\-\-\-- \-\-\-\-\-\-\-\-\-\-\-\--
\-\-\-\-\-\-\-\-\-\-\-\-- \-\-\-\-\-\-\-\-\-\-\-\--

NET: 0.00

Appendix III: Loss Code Description

[Property damage (code 1\~49)]{.underline}

1.  Intersection: Bus straight ahead - other vehicle from left

2.  Intersection: Bus straight ahead - other vehicle from right

3.  Intersection: Bus turning right - other vehicle from ahead

4.  Intersection: Bus turning right - other vehicle from left

5.  Intersection: Bus straight ahead - other vehicle from opposite
    direction turns left

6.  Intersection: Bus turning right - other vehicle from rear

7.  Intersection: Bus turning left - other vehicle from ahead

8.  Intersection: Bus turning left - other vehicle from left

9.  Intersection: Bus turning left - other vehicle from right

10. Intersection: Bus turning left - other vehicle from rear

11. Intersection: Other vehicle turns right in front of bus

12. Intersection: All other intersection collisions

13. Head-on - vehicles from opposite directions

14. Sideswipe - bus passing other vehicle

15. Sideswipe - other vehicle from opposite direction

16. Sideswipe - other vehicle passing bus

17. Cutting in - by other vehicle

18. Other vehicle pulling from curb hit bus

19. Collision with standing vehicle (includes opened doors, parked auto)

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22. All other accidents between intersections

23. Rear end - bus hit vehicle

24. Rear end - other vehicle hit bus

25. Loading zone: Bus pulling into zone involved with standing vehicle

26. Loading zone: Bus pulling from zone involved with standing vehicle

27. Loading zone: Bus pulling from zone involved with moving vehicle

28. Loading zone: Other vehicle involved with bus standing in zone

29. Loading zone: Bus pulling into zone involved with moving vehicle

30. Miscellaneous: All other collisions with other vehicles, bikes.

31. Scrapes at corners. Intersection sideswipes (includes right turn
    squeeze)

32. Sideswipes between intersections other than opposite direction

33. Opposite way sideswipes between intersections

34. Collisions between company passenger vehicles: end to end - in
    loading zones

35. Collisions between company passenger vehicles: end to end other than
    loading zones

36. Collision between company passenger vehicles: on company property,
    yards, terminal company parking

37. All other collisions between company passenger vehicles.

38. Collision with stationary object while bus backing.

39. Pedestrians - Intersection/crosswalks

40. Pedestrians - loading zones

41. Pedestrians - hit by overhang (bus turning)

42. Pedestrians - Between intersections

43. Pedestrians - all others

44. Miscellaneous collision: alleges - location - division or department
    unknown

45. Collisions with (fixed) stationary objects

46. Collision due to bus mechanical failure.

47. Collision due to bus leaving road

48. Collision not classified

49. Bus backing collision with moving vehicle.

### Passenger injury (code 50\~118)

50. Falls boarding

51. Miscellaneous boarding

52. Struck by front door - boarding

53. Falls alighting - front door

54. Handi Lift

55. Falls alighting - rear door

56. Falls alighting - rear door (push type)

57. Fall alighting not otherwise classified

58. Struck by front door - alighting

59. Struck by rear door - alighting

60. Struck by rear door - alighting (push type)

61. Struck by door not otherwise classified

62. On board: bus starting

63. On board: bus stopping

64. On board: bus turning

65. On board: bus running straight

66. On board: caught/struck by doors

67. On board: injuries from arms, head, etc. out of window

68. On board: accidents not otherwise classified

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```
70. Property damage caused by defective equipment

71. Injuries caused by defective equipment

72. Disturbances, ejectments fainting, sickness, fits, deaths on
    vehicles, etc.

73. Injuries or prop damage caused by other passengers or other person
    except bus motion

74. Falls - approaching to board or after alighting

75. Clothing soiled off bus (splashed water, etc.)

76. Thrown missiles (injuries/damage)

77. Thrown missiles (no injuries/damage)

78. Incidents not otherwise classified

79. Observation or witness reports (operator\'s vehicle not involved)

80. Non-operating vehicle accidents (supervisor cars, co. trucks,
    vehicles operated by mechanics, vandalism)

81. Other alleged

82. Other alleged

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```
88. Bicycle

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```
90. Employee accidents

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```
99. Public accidents on company property - not defined

100. Striking and injuring or killing animal

101. Wheelchair: Falls boarding

102. Wheelchair: Door hit

103. Wheelchair: Miscellaneous boarding

104. Wheelchair: Lift stand

105. Wheelchair: Lift WC PAX

106. Wheelchair: Fall alighting

107. Wheelchair: Fall alighting

108. Wheelchair: Fall alighting

109. Wheelchair: PAX start

110. Wheelchair: PAX stop

111. Wheelchair: PAX curve (turning)

112. Wheelchair: PAX straight

113. Wheelchair: PAX door

114. Wheelchair: PAX window

115. Wheelchair: On board

116. Wheelchair: Tie down

117. Wheelchair: Tie down

118. Wheelchair: Lift

### 

### Violation (code 119, 120)

119. Civil right

120. ADA violation

Appendix IV: Accident Data as Shown in Bar Charts

For Table 26 and 27 the percentages shown in black are actual cost data,
and those in blue are generated by the statistics from Agency IV and V.

Table 5 Claim and cost distributions for collision accidents with cost
less then 10K

  ------------ --------- ------------- ------------ ------------ ------------ ------------ ------------ ------------ ------------ ------------
  **Agency**   **Total   **Total       **Percent of                                        **Percent of                           
               claim**   cost**        claims**                                            costs**                                

                                       **F**        **S**        **R**        **N**        **F**        **S**        **R**        **N**

  I            324       \$665,044     29.0         55.2         11.1         4.6          36.1         49.5         11.1         3.4

                                       ***26.0***   ***48.7***   ***13.7***   ***11.6***   ***35.1***   ***44.4***   ***10.7***   ***9.8***

  II           1,109     \$1,108,053   13.3         40.8         6.3          39.5         18.5         36.6         4.0          40.9

                                       ***19.5***   ***54.4***   ***13.8***   ***12.4***   ***27.5***   ***50.8***   ***9.9***    ***11.8***

  III          346       \$263,970     16.2         46.2         24.3         13.3         20.7         51.1         15.9         12.3

                                       ***18.7***   ***44.7***   ***23.9***   ***12.7***   ***25.3***   ***45.3***   ***16.8***   ***12.6***

  IV           243       \$343,870     27.6         35.4         25.5         11.5         34.4         32.4         22.7         10.5

                                       ***24.0***   ***37.6***   ***26.0***   ***12.4***   ***30.9***   ***36.9***   ***22.0***   ***10.2***
  ------------ --------- ------------- ------------ ------------ ------------ ------------ ------------ ------------ ------------ ------------

# 

Table 6 Claim and cost distributions for all collision accidents

  ------------ --------- ------------- ------------ ------------ ------------ ------------ ------------ ------------ ------------ ------------
  **Agency**   **Total   **Total       **Percent of                                        **Percent of                           
               claim**   cost**        claims**                                            costs**                                

                                       **F**        **S**        **R**        **N**        **F**        **S**        **R**        **N**

  I            353       \$2,904,763   31.7         52.4         10.2         5.7          70.6         22.4         2.5          4.4

                                       ***29.0***   ***46.4***   ***12.6***   ***12.1***   ***70.4***   ***21.3***   ***2.4***    ***5.9***

  II           1,146     \$6,319,107   14.7         40.2         6.2          38.9         20.5         45.0         0.9          33.6

                                       ***20.6***   ***53.3***   ***13.4***   ***12.7***   ***22.1***   ***47.5***   ***1.9***    ***28.5***

  III          358       \$997,982     17.3         45.3         23.7         13.7         22.4         17.5         5.7          54.5

                                       ***19.7***   ***43.8***   ***23.4***   ***13.1***   ***23.6***   ***15.9***   ***5.9***    ***54.6***

  IV           261       \$1,032,796   29.9         34.1         24.9         11.1         61.4         19.6         14.3         4.7

                                       ***26.6***   ***36.1***   ***25.4***   ***12.0***   ***60.2***   ***21.1***   ***14.0***   ***4.6***
  ------------ --------- ------------- ------------ ------------ ------------ ------------ ------------ ------------ ------------ ------------

# 

# 

[Table 7 Transit agencies: General collision accident costs by initial
point of impact]{.underline}

  ------------ --------- -------------- ----------- ------- ------- ------- ----------- ------- ------- -------
  **Agency**   **Total   **Total        **Percent                           **Percent                   
               claim**   costs**        of claims**                         of costs**                  

                                        **F**       **S**   **R**   **N**   **F**       **S**   **R**   **N**

  I            348       \$1,186,535    31.0        52.9    10.3    5.7     45.2        37.8    6.2     10.7

  II           1,137     \$1,826,183    14.4        40.4    6.2     39.0    31.2        31.8    3.0     34.0

  III          357       \$543,490      17.4        45.4    23.8    13.4    41.1        32.1    10.4    16.4

  IV           260       \$796,180      29.6        34.2    25.0    11.2    49.9        25.5    18.5    6.1

  V            1,731     \$3,098,536    25.2        48.1    16.2    10.6    18.4        18.8    1.8     20.0

  CalTIP(30)   1,391     \$3,339,754    22.5        43.4    19.0    15.1    38.2        29.4    8.5     24.0

  All (35)     5,224     \$10,790,680   22.2        44.6    15.3    17.9    40.2        33.4    8.2     18.1
  ------------ --------- -------------- ----------- ------- ------- ------- ----------- ------- ------- -------

[Table 8 Transit agencies: General collision accident costs by collision
object]{.underline}

  ------------- ---------- -------------- ----------- ------- ------- ------- ----------- ------- ------- -------
  **Collision   **Total    **Total        **Percent                           **Percent                   
  object**      claims**   costs**        of claims**                         of costs**                  

                                          **F**       **S**   **R**   **N**   **F**       **S**   **R**   **N**

  Vehicle       4,762      \$9,313,621    22.6        46.0    16.2    15.2    41.3        34.6    9.2     14.9

  Pedestrian    184        \$1,027,244    26.3        17.5    1.6     54.6    37.2        21.4    0.2     41.2

  Stationary    278        \$449,815      12.4        38.8    9.5     39.2    24.7        35.7    6.7     32.9
  object                                                                                                  

  Total         5,224      \$10,790,680   22.2        44.6    15.3    17.9    40.2        33.4    8.2     18.1
  ------------- ---------- -------------- ----------- ------- ------- ------- ----------- ------- ------- -------

# 

[Table 9 Transit agencies: General vehicle collision costs by accident
scenario]{.underline}

  ------------ ---------- ------------- ----------- ------- ------- ------- ----------- ------- ------- -------
  **Accident   **Total    **Total       **Percent                           **Percent                   
  scenario**   claims**   costs**       of claims**                         of costs**                  

                                        **F**       **S**   **R**   **N**   **F**       **S**   **R**   **N**

  S1           668        \$1,697,209   31.5        49.0    5.1     14.4    40.2        43.1    4.9     11.9

  S2           461        \$2,174,890   100.0       0.0     0.0     0.0     100.0       0.0     0.0     0.0

  S3           486        \$432,289     0.0         0.0     100.0   0.0     0.0         0.0     100.0   0.0

  S4           852        \$1,243,354   12.0        55.8    5.8     26.5    22.7        52.0    4.5     20.8

  S5           752        \$935,215     0.0         100.0   0.0     0.0     0.0         100.0   0.0     0.0

  S6           230        \$340,937     25.2        49.3    4.5     20.9    31.5        50.4    6.2     11.9

  S7           432        \$407,126     19.6        48.4    22.8    9.1     13.8        44.8    23.8    17.5

  S8           382        \$873,890     12.6        42.1    12.9    32.3    28.2        34.8    5.3     31.7

  S9           499        \$1,208,711   22.0        31.0    9.0     38.1    18.9        28.3    9.8     43.0

  **Total**    4,762      \$9,313,621   22.6        46.0    16.2    15.2    41.3        34.6    9.2     14.9
  ------------ ---------- ------------- ----------- ------- ------- ------- ----------- ------- ------- -------

[Table 10 Transit agencies: Passenger injuries by bus
movements]{.underline}

+-------------------+--------+---------------+-----------+-----------+
| **Bus movement**  | **C    | **Cost**      | **Percent | **Percent |
|                   | laim** |               | of        | of        |
|                   |        |               | claims**  | costs**   |
+-------------------+--------+---------------+-----------+-----------+
| # Boarding        | 499    | \$1,013,907   | 11.6      | 7.5       |
+-------------------+--------+---------------+-----------+-----------+
| Alighting         | 770    | \$1,816,013   | 18.0      | 13.4      |
+-------------------+--------+---------------+-----------+-----------+
| Starting          | 168    | \$567,644     | 3.9       | 4.2       |
+-------------------+--------+---------------+-----------+-----------+
| Stopping          | 849    | \$3,820,606   | 19.8      | 28.1      |
+-------------------+--------+---------------+-----------+-----------+
| Turning           | 115    | \$387,192     | 2.7       | 2.9       |
+-------------------+--------+---------------+-----------+-----------+
| Going straight    | 136    | \$521,322     | 3.2       | 3.8       |
+-------------------+--------+---------------+-----------+-----------+
| Moving (others)   | 561    | \$2,259,218   | 13.1      | 16.6      |
+-------------------+--------+---------------+-----------+-----------+
| Others            | 1,187  | \$3,199,336   | 27.7      | 23.6      |
+-------------------+--------+---------------+-----------+-----------+
| **Total**         | 4,285  | \$13,585,239  |           |           |
+-------------------+--------+---------------+-----------+-----------+

#