VI. COSTS and LEAD TIMES
These preliminary estimates are NHTSA-derived estimates mainly based on confidential discussions with a variety of suppliers and manufacturers about how their systems work and the various components in their systems. In addition, NHTSA has the preliminary results of a tear-down study of costs by a contractor of two direct measurement systems. All costs provided here are consumer costs. Variable cost estimates received from suppliers were multiplied times 1.51 to mark them up to consumer cost levels. These cost estimates assume high production volumes, since these systems will be required to go on 16 million vehicles. For this analysis, we estimate there will be sales volumes of 16 million light vehicles per year, 8 million passenger cars and 8 million light trucks.
Indirect measurement systems:
There are different ways of using indirect measurement systems for a Tire Pressure Monitoring Systems (TPMS). The first assumes that the vehicle has an existing ABS system and that manufacturers will add the capability to monitor the wheel speed sensors, make changes to the algorithms, add the ability to display the information and a reset button. The incremental cost of adding these features to an existing ABS vehicle is estimated to be approximately $12 per vehicle. Currently about two-thirds of all new light trucks and passenger cars have ABS systems. NHTSA tested four current ABS-indirect measurement systems and none of the four met the proposed requirements to provide a driver warning at 25 percent below placard and to detect "one, two, or three tires" being low. They had problems detecting two tires low on the same axle or when two tires on the same side of the vehicle were low. The agency anticipates changes in the algorithms at a cost of $2 per vehicle to compare relative wheel speeds could be used to determine when one, two, or three tires are different from the others. However, the system wouldn't be able to detect when all four tires slowly lose air at about the same time and are low. The agency does not know whether there will be additional costs to improve the accuracy of the current ABS indirect measurement systems from roughly 30 percent below placard to the proposed upgraded 25 percent below placard. Comments are requested on the cost estimates.
If the agency decides it is important to also measure when all four tires are low, then the current ABS indirect measurement system would have to add another feature to independently determine vehicle speed (independent of the speedometer that works off wheel speed), so that individual tire speeds could be compared to vehicle speed. Although the agency has not tried it to determine its accuracy, a GPS system is the least costly possible method of independently determining vehicle speed. Other measures the agency could think of, adding a fifth wheel or a radar system, are either impractical or too costly.
Pickup trucks comprise about 40 percent of light truck sales. Some proportion of pickup trucks (comments are requested on this percent) that have ABS, have only one wheel speed sensor for the rear axle. In order to pass the proposal that the system be able to detect when one, two, or three tires are low, the agency believes these trucks would have to add a fourth wheel detector at a cost of $20 per vehicle. The agency assumes for this analysis that about 10 percent of all light trucks, or 7.5 percent of all light vehicles with ABS, would be in this category.
For those vehicles without ABS, there are two ABS-based indirect measurement choices. The first is not adding a full ABS system, but just those parts of the system needed for a TPMS system. Essentially, this would require adding TPMS and wheel speed sensors, which will cost approximately $130 per vehicle. (The agency won't discuss this option further, since it is more costly than a direct measurement system.)
To add the full ABS system (a manufacturer's marketing decision, not a NHTSA requirement) and a TPMS will cost approximately $240 per vehicle. (Again, the agency won't discuss this option further, since it is more costly than a direct measurement system, and it is a marketing decision by the manufacturer to spend more money to get a full ABS-system.)
Direct measurement systems:
A direct measurement system has a pressure sensor inside each tire that broadcasts tire pressure, and in some systems internal air temperature, to a central receiver on the vehicle (or in some cases to four separate antennae on the vehicle which relay the data to a central processor). It sends the information to a central processor that in turn displays a low-pressure warning when appropriate. Thus, there can be two main costs of these systems (sensors and a receiver/central processor).
There is a wide disparity in costs for the sensors depending upon what type of information is sensed. Providing just the information proposed to be required by the NPRM (tire pressure) would cost in the range of $5 to $10 per wheel (or $20-40 per vehicle for this analysis). Some systems can sense tire pressure and air temperature inside the tire.
The cost for the receiver/central processor depends upon whether the current vehicle already has a receiver capable of receiving/processing the information coming from the sensors or not. It is estimated that about 60 percent of vehicles currently have the capability to receive the information (some in the form of a keyless remote entry system) and process the information. With some software changes and adding a display, showing tire pressure for all four tires individually, at a cost of about $25 per vehicle, these systems with the added cost of sensors could meet the proposal. Other vehicles that currently don't have a receiver/central processor (about 40 percent of the vehicles), would have to add them and the software and a display at an estimated cost of about $40 to $50 per vehicle.
An additional cost is the installation of the direct measurement system to the vehicle, which is estimated to cost about $4 per vehicle.
The agency also has a teardown study in progress performed by its contractor Ludtke & Associates. (1) Two direct measurement systems, the Beru tire pressure warning system and the Johnson Controls system, have been torn down and costed out to date.
The Beru system is an expensive system that goes beyond the bare minimum needed to pass the alternative. The Beru system is capable of providing a "soft warning" with an amber telltale lamp when the inflation pressure drops 2.8 or more psi below the recommended pressure, and a "hard warning" with a red telltale lamp when the under-inflation is 5.7 psi or greater below the recommended inflation pressure.
The costs of the Beru direct measurement system are broken into the following categories (1 control unit at $130, 4 wheels electronic modules to measure tire pressure and transmit the data at $33, 4 reception antenna at $26, 4 valves at $1, assembly at $4, and miscellaneous costs at $6, for a total of $200).
The costs of the Johnson Controls direct measurement system are broken into the following categories (1 control unit at $31, 4 wheels electronic modules to measure tire pressure and transmit the data at $33, 1 reception antenna at $1, 4 valves at $1, assembly at $2, for a total of $68).
A direct measurement system with a pump:
Cycloid Company makes a pump based system that uses 4 wheel electronic modules, like a direct measurement system, as well as a pump to inflate the tires to proper pressure while the vehicle is being driven. Each tire has a sensor and a pump. The pump is attached under the hubcap. The display is designed to give a warning to the driver when a particular tire has a problem and needs servicing. For slow leaks, the pump can keep inflating the tire enough to get the vehicle to its destination. However, once the vehicle stops, the pump stops, and the tire will deflate. The cost of this system is estimated to be the same as a sensor-based system, except that there is the addition of a pump at an estimated cost of $10 per wheel, or $40 per vehicle. The benefit of this system is that it eliminates the need for the driver to stop for air for normal tire pressure loss conditions.
Table VI-1 shows the estimated incremental costs for the different types of systems
Cost Summary of TPMS Costs
|Indirect Measurement System|
|Add to Existing ABS||$12|
|Adding Wheel Sensors||$130|
|Adding Full ABS||$240|
|Changing Algorithms of Current ABS-TPMS||$2|
|Adding Fourth Wheel Speed Sensor Capability for Some Pickups||$20|
|Direct Measurement System|
|With Current Receiver/central processor||$49 to $69 (we will use the mid-point $59)|
|Without Current Receiver/central processor||$64 to $94 (we will use the mid-point $79)|
|With a Pump, with current receiver/central processor||$89 to $109|
|With a Pump, without current receiver/central processor||$114 to $134|
Current TPMS Systems in New Vehicles
Current use of TPMS in new vehicles was determined by using the calendar year 2000 sales, a model year 2001 list of the make/models with each type of system, and an estimate that 2 percent of sales were purchased as an option for those optional systems, to estimate the percent of the year 2000 sales that had each type of system. The resulting estimates are that 4 percent of the model year 2001 light vehicle fleet has an ABS-type indirect measurement TPMS, or 6 percent of the ABS fleet has a TPMS, and 1 percent of the fleet has a direct measurement system. While there are cost implication to make the current indirect TPMS comply with Alternative 2 (estimated at $2), the agency believes the direct systems could be changed at no cost to meet Alternative 1.
System Cost Summary by Alternative
Alternative 1: Assuming a direct measurement system is required, the incremental cost would be an estimated $66 per vehicle ($59 with current receiver/central processor * 60 percent with receiver/central processor + $79 without receiver/central processor * 40 percent without receiver/central processor = $67 per vehicle * 99 percent to account for the 1 percent of sales in the current fleet = $66.33)
Alternative 2: An indirect measurement system for all passenger cars and light trucks with ABS, is estimated to cost an average ABS-equipped light vehicle $12.90 per vehicle ($12*0.94 + $2*.06 + $20 *0.075 = $12.90). This accounts for 94 percent of the ABS systems have no TPMS, 6 percent have TPMS and 7.5 percent need a fourth wheel sensor. The overall cost for Alternative 2 assuming that an indirect system would be provided for the 67 percent of the fleet that is already equipped with ABS, and that a direct measurement system will be installed in the remaining 33 percent of the fleet is estimated to be $30.54 ($12.90 * .67 + $66.33*.33).
The agency anticipates that there will be maintenance costs associated with both a direct and an indirect measurement system. Most notable to consumers for most ABS-type indirect systems is a reset button that must be pushed whenever the tires have been rotated and perhaps when tires have been inflated. There is the potential for the reset button to be misused, just to get the warning light to go out, before inflating the tires and then forgetting to inflate the tires. In addition, the agency is aware of problems with wheel speed sensors with mis-adjustment, maintenance, and component failures.
The direct measurement systems also have maintenance concerns. Because there are sensors in the wheel, they can be damaged when tires are changed, etc. Furthermore, there is a battery in the sensor in most systems, which has a finite life of about 10 years currently, that will have to be eventually replaced to keep the system functioning.
The agency has not attempted to estimate these maintenance costs and requests comments on them. These costs are real, but they will decrease as improvements keep being made to the systems.
More frequent tire inflation costs
In order to benefit from the TPMS, drivers must respond by maintaining the air pressure in their tires. To accomplish this, they must either make a separate trip to a service station to get the air, or spend additional time to fill their tires when they are at the station getting gasoline. The process of checking and filling tires is relatively simple and would probably take from 3-5 minutes. The time it takes to make a separate trip to a gas station would vary depending on the driver's proximity to a station at the time they were notified. Presumably, the greater the distance to the station, the less likely the driver would be to make a separate trip.
It is likely that drivers who take action to fill their tires would consider this extra time to be fairly trivial. Since the action is voluntary, by definition, they would consider it to be worth the potential benefits they derive from properly inflated tires. However, when tallied across the entire driving population, the total effort involved in terms of man hours may be significant. Tires lose an estimated 1 psi per month, which means they lose 6 psi every 6 months. Therefore, people who otherwise would never fill their tires would be notified about twice a year. However, since many people do check their tires more frequently than that, the average number of extra fill ups would be considerably less than 2 per year. NHTSA has no data to indicate what portion of drivers would make a separate trip, or wait to fill their tires when they next filled their gas tanks.
The test to show compliance may be broken down into the following sets of tests. Initially the vehicle would be set up for the test with each of the four wheels being instrumented. The vehicle would be run for a specified time to check out the system. Then, one tire would be deflated and the vehicle driven for 10 minutes to determine the response. Each of the other three tires would be deflated separately and the response of the system checked. Then, different combinations of two tires would be deflated at a time and the vehicle driven for ten minutes, different combinations of three tires would be deflated at the same time and finally all four tires would be deflated at the same time. Before and during these tests, the system may need to be calibrated. The agency has not worked out the calibration procedure yet, but for these estimation purposes, assumes it would take several hours. Finally, the agency is considering running a system failure test, if required by the standard, where some part of the system would be disconnected to determine whether there was an indication of system failure. The data must be collected, analyzed and a test report written.
Assuming one set of tires on one vehicle at one vehicle load, the man-hours for the test are 6 hours for a manager, 30 hours for a test engineer and 30 hours for a test technician/driver.
Labor costs are estimated to be $75 per hour for a manager, $53 per hour for a test engineer and $31 per hour for technicians. Total testing costs are thus estimated to be $2,970 ($75 * 6 + $30 * 53 + $31 * 30). If for light trucks, it is necessary to test the vehicle unloaded and fully loaded, the test costs for light trucks would essentially double.
The act requires that the effective date of the rule be two years after the final rule. If Alternative 1 is selected then the manufacturers would be required to provide direct measurement systems in all vehicles. Comments are requested on whether there would be enough supply of direct measurement systems for 16 million vehicles at one time. However, if Alternative 2 is selected for the final rule, the agency believes that both suppliers and vehicle manufacturers can be ready to provide TPMS given the two-year lead time.
1. 1 Beru Tire Pressure Warning System, for No. DTNH22-00-C-02008 Task Order No. Three (3).