In 2002, Trimble Navigation Ltd. developed the Telvisant DriveSafe Driver Safety Scorecard in response to a proposal from the McNeilus Cos. to design a product — featuring low acquisition and operating costs, yet simple to install and maintain — that would allow early detection of unsafe driving habits. Inherent in the ready-mixed concrete industry are driver safety and truck rollover issues, which have a critical impact on equipment operating costs and profits. Lost productivity is only one of many expenses resulting from unsafe driving behaviors that lead to accidents. Repair costs, higher insurance rates, and higher fuel, tire and maintenance costs can be significant liabilities as well.

A complete solution that provides vehicle owners and fleet managers reports detailing drivers' operation of their vehicles, the DriveSafe system includes features such as:

• A truck-based mobile unit containing a computer processor, a GPS receiver and a wireless modem;
• Web-accessed data analysis;
• Report generation software; and,
• A secure database.

DriveSafe measures the accelerations exerted on the truck during various driving maneuvers (turns, starts, stops, etc.) and compares these measurements to the average for the customer's fleet or to the industry as a whole. Scores are calculated for several categories of maneuvers, and the individual scores plus a composite Driver Score are reported. Mixer drum speed (if the truck is equipped with a drum-speed sensor) and vehicle speed are also considered.

USING THE SCORES

Because DriveSafe provides a record of individual driver behavior beyond mere driving speed by including indicators of other, less conspicuous forms of aggressive driving, supervisors can use this tool to conduct specifically targeted driver training and counseling programs. In many cases, otherwise competent drivers simply need to be reminded of certain driving practices, such as preparing to stop when the truck is loaded. In other cases, drivers need training to significantly alter their driving style when the truck is loaded in order to avoid potential rollover situations. The driver scores are accumulated over a long period of time, allowing transparency in trends of driving behavior.

DriveSafe is not a direct, near-accident-event indicator. According to Trimble, the Scorecard is designed to assist in training and monitoring, and should not be used to penalize a driver for one or two hard maneuvers that may have been necessary due to the careless behavior of others on the road. Accordingly, the reports should always be run using a one-week period at least — and preferably longer.

DRIVESAFE REPORTS

DriveSafe reports contain individual scores for each driving maneuver, plus a weighted composite score for the vehicle. The data can be presented and printed in a tabular Fleet Report and an easy-to-read Fleet Chart. Exporting data in a format compatible with standard data analysis tools such as Microsoft Excel is also an option.

A vehicle's performance can be scored against the performance standard for the fleet or against the performance standard for the industry as a whole. The selection of the performance standard is made when the report is run.

For scoring purposes, fleet standards are calculated on the basis of all available data for a given fleet, and data from all available fleets are used for the national standard. A standard is calculated for each driving maneuver. The standard itself comprises a mean and a standard deviation for the acceleration values in question.

Vehicle scores are calculated by comparing the vehicle data to the standard used for the report. If the vehicle's acceleration data matches the standard, the score is set to 100. One standard deviation in the standard's data is assigned a value of 10 points, so if the vehicle's acceleration is higher than the standard's average by one standard deviation, the score is 110. For data two standard deviations below the standard, the score is 80. The data are assumed to follow a statistical “normal distribution,” so 98 percent of all scores may be expected to fall between 70 and 130.

Before running a report, several settings must be indicated. The report type can be Fleet Report or Fleet Chart. The range of dates over which the report is run, the vehicles to be included in the report, and the standard against which the vehicles are scored (Fleet or National) must be selected. The Quick Time Range helps in quickly selecting the date range, and Vehicle Lists may be defined to select groups of vehicles.

Clicking the Generate Report button displays the report or chart on the screen. Subsequently, the report can be printed using the printer icon or exported to a file on the local computer using the disk icon.

With the Score Configuration button on the Report Options screen, two configuration items can be set. The first is the Score Weighting value, which defines the contribution of each of the maneuver types to the composite driver score. If, for example, loaded right turns are considered to be five times as important as unloaded starts, the LoadedRightTurn value should be set to 5 and the UnloadedStart value to 1. The weights can be set to any value, including zero, and do not need to add up to any particular sum. Since changing these values can change the relative positions of different vehicles, the weights used are printed on the report itself.

Good practice generally dictates that once a set of weights is defined, it should not be changed arbitrarily. However, different sets of weights may be appropriate for different purposes. A report that is intended for driver safety, for example, may have one set of weights, while a different set of values might be needed for a more equipment-oriented report that places a higher weight on those maneuvers causing excessive tire wear or engine over-revving.

The second configuration item is the Highlight Threshold. Scores that are greater than or equal to these settings are highlighted in yellow on the reports and appear in red on the charts.

HOW DRIVESAFE WORKS

By way of raw data collection, the firmware in the mobile unit collects data in several categories. The basic data value is an acceleration derived from a change in velocity measured by GPS. Acceleration values are measured for different maneuvers under different vehicle conditions in the following categories:

Maneuver	Vehicle Loaded	Vehicle Unloaded
Start	X	X
Stop	X	X
Right turn	X	X
Left turn	X

When a maneuver has been detected and is complete, the maximum acceleration reached in that maneuver is saved for processing. The vehicle is determined to be loaded between the time the mobile unit detects loading at a home site and the time that a pour is noted at a job site. The unloaded condition is between the pour and the next loading.

The DriveSafe firmware in the mobile unit also gathers vehicle speed data. The speed is sampled once per second and the maximum speed over the past minute is determined. A counter in the speed category corresponding to this maximum speed is incremented.

As with all DriveSafe data, reporting over a broad period of time is meant to ensure that all drivers will encounter similar jobs and driving conditions, and that an average vehicle speed for all driving will be relevant.

The data collection algorithm also corrects for missing data due to short GPS dropouts and errors that may occur during satellite constellation changes. Wireless communication fades do not affect the system, as data are retained and reliably sent when the vehicle returns to a better coverage area.

With respect to data processing in the vehicle, a set of data “bins” is reserved for each category of information. Each bin contains a count of the occurrences of an acceleration value in a particular range. After the maximum acceleration for a maneuver has been calculated, the count in the bin in which the acceleration falls is incremented.

DriveSafe also considers the effect of the mixer drum speed on truck stability during right turns. Given the dynamics of concrete in the drum, a higher drum speed makes right turns more susceptible to safety issues. This effect is factored into the data by incrementing the bin for a higher acceleration than that actually measured. Above a maximum acceptable drum speed, the measured acceleration is increased proportionally to the excess drum speed, causing the driver's right turn to be recorded as having a higher acceleration.

The counts in the acceleration bins are transmitted to the database when the truck's ignition is turned off. Data transmission is accomplished automatically using wireless communications without operator intervention and without any manual data-gathering procedures. After the data is transmitted to the database, bin counts are cleared.

Overall processing of bin data to determine a vehicle score is illustrated in the accompanying flow chart. On a maneuver-by-maneuver basis, bin weighting is applied to the counts in each bin before further processing is done. The value in each bin is converted from a count to a weighted acceleration.

Once the bins are weighted, the accelerations in all bins for a given type of maneuver are added to determine a single average acceleration value for that maneuver for that vehicle for that time period. The number of data points and the weighting are retained and carried along with the average for analytical and historical documentation purposes.

DriveSafe data is stored in Trimble's Telvisant database, which is hosted in a secure data center for a high level of reliability and data access control. Each customer can view only their own vehicles' data, and access to the DriveSafe portion of the database is controlled on a user-by-user basis within the customer's staff.

HOW DRIVESAFE IS DEPLOYED

Convenience in deploying the DriveSafe system is one of its primary advantages. Once hardware is installed in the vehicle, Trimble configures the hardware over the air, data are collected for at least two weeks, and the Web reports are run. The reports can be accessed either from a stand-alone Web site for DriveSafe-only customers or as a Reporting menu option for Trimble's AutoStatus customers.
— information provided by Trimble Navigation Ltd., drivesafe@telvisant.com

Note: GPS/wireless communication-enabled vehicle status and location tracking systems have been widely recognized for offering ready mixed producers new levels of fleet management and cost control. In addition to automated status and location recording, these systems can also be adapted to monitor safe and unsafe driving practices. Here, Concrete Products presents background on the DriveSafe technology that McNeilus Cos. and Trimble Navigation Ltd. unveiled last month at the National Ready Mixed Concrete Association's Operations, Equipment & Safey Forum & Expo in Denver. Recognizing that driver safety is an industry-wide concern, NRMCA has provided a link, from www.nrmca.org, to this overview from Trimble. DriveSafe coincides with NRMCA's concerted educational effort to change behavior leading to rollovers and other mixer truck accidents, and instill new professionalism among vehicle operators (note CDP report, page 30).