Driving workload estimation

[0001] The present disclosure relates generally to driving workload estimation and in particular, to a method of assessing the marginal effect of vehicle conditions, environment conditions and current task conditions on the driver of a vehicle.

[0002] Vehicles, such as automobiles, generally feature one or more displays to provide locally obtained information related to a current state of the vehicle. The display is positioned within the vehicle such that a driver of the vehicle may view information while driving the vehicle. For example, the display may provide information on a windshield, a dashboard or a steering wheel. Each display may contain one or more windows. Locally obtained information, such as the speed of the vehicle, the direction traveled by the vehicle, the outside air temperature, whether the air conditioner is in use, whether the hazard light is on, fuel status of the vehicle, and the like, may be provided in these windows. In addition, information can be collected from vehicle sensors and used to create vehicle status and maintenance messages for display in the windows. These messages can include information such as “window washer fluid low” and “check tire pressure.”

[0003] The current displays in vehicles are capable of providing different types of media from a variety of sources. The display may provide audio, text, graphic images, and/or video (e.g., night vision display). Additionally, the display may provide information from various databases and remote servers using a wireless network. For example, traffic and/or weather alerts may be communicated through any of the display means mentioned above. In addition, smart advertising may be transmitted to the display to inform the driver of a nearby restaurant or store. Providing all of these types of information and media may be helpful to the driver but providing it without considering the current driving situation may result in increased driver workload, driver distraction and/or decreased driving performance.

[0004] The above discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by a method for estimating workload placed on the driver of a vehicle. In an exemplary embodiment, the method comprises receiving workload estimation data. A driving workload estimate is calculated in response to the workload estimation data. The driving workload estimate is indicative of current and previously occurring conditions. The driving workload estimate is then output.

[0005] In another aspect, a system for estimating workload placed on the driver of a vehicle comprises a network and a microprocessor in communication with the network. The microprocessor includes instructions to implement a method. The method comprises receiving workload estimation data from the network. A driving workload estimate is calculated in response to the workload estimation data. The driving workload is indicative of current and previously occurring conditions. The driving workload estimate is then output.

[0006] In still another aspect, a computer program product for estimating workload placed on the driver of a vehicle comprises a storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method. The method comprises receiving workload estimation data. A driving workload estimate is calculated in response to the workload estimation data. The driving workload estimate is indicative of current and previously occurring conditions. The driving workload estimate is then output.

[0011] Disclosed herein is a method of driving workload estimation. Briefly stated, the method utilizes vehicle data, environment data and current task data to estimate the workload placed on the vehicle driver. A conditional model of the driver's workload (herein identified as driving workload) is developed by assessing the marginal effect of the vehicle, environment and current tasks on the driver. Multiple levels or states of the driving workload are estimated by workload estimation software. In an exemplary embodiment, the estimated workload states include an instantaneous workload estimate, an intermediate workload estimate and an overall workload estimate. Alternatively, the system can utilize a single workload estimate, provided that some method of accounting for the lingering impact of events and conditions that are no longer occurring is taken into account by the workload estimate. These estimated workload states are output and can be sent to a vehicle information management system to aid in controlling the messages being sent and the functionality available to the operator of the vehicle.

[0012] FIG. 1 is a block diagram of an exemplary system for performing driving workload estimation. Vehicle data 104, environment data 106 and current task data 108 are input to a driving workload estimator 102. The driving workload estimator 102 includes application code for creating an instantaneous workload estimate 110, an intermediate workload estimate 112 and an overall workload estimate 114. In an exemplary embodiment, the driving workload estimator 102 is located on a microprocessor contained in the vehicle. The microprocessor may be dedicated to performing driving workload estimator 102 functions or, alternatively, the microprocessor may include application code for performing other vehicle functions along with the driving workload estimator 102 functions. In addition, storage space for intermediate application results as well as application inputs and outputs can be located on the microprocessor or located on an external storage device accessible by the microprocessor.

[0013] Vehicle data 104 is internally generated and is received from sensors located inside the vehicle. Vehicle data 104 can include information such as vehicle speed, cruise control state, turn signal status, traction control status (TCS), antilock braking system (ABS) status, vehicle stability system data, powertrain data, steering wheel angle, brake pedal position and throttle pedal position data. Powertrain data can include information such as revolutions per minute (RPM), spark data and fuel data. Environment data 106 can include external light sensor/headlamp status data, wiper status, defroster status, outside air temperature (OAT), global positioning system (GPS) data, time of day, and enhanced digital maps. Current task data 108 includes data such as radio information (e.g., is manipulation occurring) and phone information (e.g., is the phone active). In addition, driver identification input to the driving workload estimator 102 can be used to tailor the workload estimates to a particular driver of the vehicle. Additional input can include driver monitoring data and input that is scalable to the vehicle sensor set and the equipment package (e.g., navigation, imbedded cell phone). Driver monitoring data includes the ability for the driver, or the vehicle system to revise the driving workload estimate. Additional input data can also include information from an object detection and warning and/or lane sensing application or sensor. Examples include forward collision warning (FCW) data, side object detection (SOD) data, lane departure warning (LDW) data and rear collision warning (RCW) data. Further input to the driving workload estimator 102 can include infotainment and telematics system status; speech interface status and diagnostics data; and adaptive cruise control (ACC) system data.

[0014] The specific inputs to the driving workload estimator 102 can vary between implementations depending on the input data available in a particular vehicle and the requirements of a particular implementation. A network can be used to obtain the data and the network can be internal to the vehicle or the network can provide access to information outside the vehicle. Any information that can be sensed, measured or input through an interface (e.g., wireless network) can be used as input to the driving workload estimator 102. Environment data 106 can be expanded to include information such as vehicle location data; external vehicle location data; traffic information both present and predicted; and weather information both present and predicted. As depicted in FIG. 1, three workload estimates are output from the driving workload estimator 102. The workload estimates are updated on a periodic basis and include numeric values that reflect relative workload levels. The workload estimate can be relative to a starting state such as clear driving at normal speed or driver workload when the vehicle is stationary. In an alternate embodiment, data in addition to the numeric values may be included in the workload estimates.

[0015] The instantaneous workload estimate 110 is based on a short-term time frame (e.g., the preceding zero to three seconds). For example, a turn signal coupled with a particular steering wheel angle may indicate that the vehicle is turning. The act of turning would have an impact on the instantaneous workload because it will add to the current driving workload and is generally completed in a few seconds. The intermediate workload estimate 112 is a workload based on an intermediate time interval (e.g., twenty seconds to one minute, three seconds to three minutes, three seconds to ten minutes). The intermediate workload estimation will carry a declining balance input on workload estimates for recent events. For example, if the input data indicates that the driver has just merged into traffic or that the ABS brake system is activated, the intermediate workload estimate 112 would reflect these events for a specified intermediate time interval. This may be implemented by having the estimator initiate a sub-routine that causes the workload estimate to remain above the starting state due to the fact that the effect of an ABS event does not end as soon as the ABS stops being activated. An event that affects the intermediate workload estimate 112 includes some recovery time for the driver and this is reflected in the length of time that the workload estimate continues to reflect the occurrence of the event.

[0016] The overall workload estimate 114 includes long term workload or total workload accumulated during an ignition cycle (e.g., from three minutes and up, ten minutes and up, entire ignition cycle). For example, the length of time that the driver has been operating the vehicle can be factored into the overall workload estimate 114. In an exemplary embodiment, each workload estimate is associated with from three to one hundred workload level values. In an alternate embodiment, hundreds or thousands of workload level values may be associated with each workload estimate.

[0017] The input data depicted in FIG. 2 can be utilized by a driving workload estimator 102 to calculate the driving workload estimate as a function of vehicle data 104, environment data 106 and current task data 108. Referring to the vehicle data 104 in FIG. 2, the value of vehicle speed 202 can be calculated based on the current speed of the vehicle and whether the driver is accelerating or decelerating. The value of turn signal status 204 can be determined based on whether the turn signal is activated. The value of ABS/TCS/ stability system data 206 can be calculated from sensor data gathered from dynamic vehicle controls such as the wheel speed sensors. The steering wheel angle data 208 is determined by sensors capable of determining the rate of vehicle turning. Brake and throttle pedal position data 210 can be determined by the data gathered from sensors such as the throttle position sensor (TPS) and brake pedal switch or sensor. The value of engine RPM/spark/fuel data 212 (powertrain data) can be calculated from engine management sensors and data (e.g., the TPS).

[0018] Referring to the inputs relating to environment data 106 in FIG. 2, the value of headlamp status 214 can be determined by either the external light sensor or by data from the headlamp controls. The value of wiper status 216 can be determined by either a rain sensor or the wiper controls. The value of defroster status 218 can be determined by the defroster controls. The outside air temperature (OAT) data 220 can be determined by a sensor dedicated to that purpose. Global positioning data 222 is determined by accessing data from the global positioning system within the vehicle network. Time of day 224 is determined from the clock data within the vehicle. Referring to the inputs relating to current task data 108 in FIG. 2, radio information 226 is determined by accessing vehicle data regarding radio feature and function activity. Phone status 228 is determined by accessing existing vehicle data pertaining to an integrated cellular phone system. The values associated with the input data in FIG. 2 is input to a function. The function is located in the driving workload estimator 102 and it utilizes the input data to determine the instantaneous workload estimate 110, the intermediate workload estimate 112 and the overall workload estimate 114.

[0019] FIG. 3 is a table of logical operands associated with driving workload estimation for use by a function to calculate a driving workload estimate in an exemplary embodiment of the present invention. The logical operands are used to create a framework and to set initial weightings of the driving workload estimation and can be modified to fine tune the driving workload estimator 102. A workload estimate is calculated to reflect an instantaneous workload estimate 110, an intermediate workload estimate 112 and an overall workload estimate 114 based on assigning numeric values to each of the conditions depicted in FIG. 3. Numeric values and inputs can be the same for all three workload estimates or they can vary. As shown in FIG. 3, the value of the relative workload effect associated with vehicle speed 202 can be calculated by assigning a numeric value to the results of applying the vehicle speed equations 302. A vehicle traveling between twenty miles per hour and fifty miles per hour can be given a higher speed value than a car traveling between zero miles per hour and twenty miles per hour. Similarly, a vehicle traveling between fifty miles per hour and seventy miles per hour can be given a higher speed value than a car traveling between twenty miles per hour and fifty miles per hour. A vehicle traveling over seventy miles per hour can be given a higher speed value than a car traveling between fifty miles per hour and seventy miles per hour. The value of the relative workload for turn signal status 204 can be calculated by assigning a higher numeric value if the turn signal is activated than if the turn signal is not activated, as reflected in the turn signal status equations 304. As shown in the ABS/TCS/stability equations 306, situations where the ABS, TCS and/or vehicle stability system are active can be given a higher value than when they are not.

[0020] Referring to FIG. 3, the value of the relative workload for external conditions including headlamp status 214, wiper status 216, outside air temperature 220 and time of day 224 can be calculated by assigning numeric values to the results of applying the corresponding equations. Night can be given a higher relative value than day as reflected in the headlamp status equations 308, precipitation can be given a higher relative value than no precipitation and snow can be given a higher numeric value than rain as reflected in the wiper status equations 310 and the outside air temperature equations 312. The relative value associated with time of day 224, as reflected in the time of day equations 314, can be calculated by assigning higher numeric values as the current time gets further away from noon and closer to midnight. In an alternate embodiment, the value for time of day can be calculated as a sinusoidal cycle with the peak weighting from eleven p.m. to one a.m. and the baseline from noon to one p.m. The relative value associated with the radio information 226 can be calculated using the radio task data equations 316 where the act of manipulating the radio is given a higher relative value than when no radio manipulation is taking place. Similarly, the relative workload value associated with phone status 228 can be calculated by assigning a higher relative value to phone dialing and conversations than to the absence of phone activity. This is reflected in the phone status equations 318.

[0021] In an alternate embodiment of the present invention, information from more than one input is utilized to create the workload estimates. For example, the workload estimate can take into account snowy roads if the temperature is below freezing and the windshield wipers are turned on. Additionally, if the ABS brake system is activated then the estimate can take into account the road conditions associated with snowy roads. These kinds of cross grouping combinations can lead to a better estimate of the driver workload. The time span that each value continues to be counted towards a driving workload estimate can depend on whether the workload estimate is an instantaneous workload estimate 110, an intermediate workload estimate 112 or an overall workload estimate 114. For example, the function to calculate an intermediate workload estimate 112 would continue to count the use of ABS or TCS for a specified period of time (e.g., twenty seconds to one minute) while the function to calculate the instantaneous workload estimate 110 would count the use of ABS or TCS for a shorter period of time (e.g., zero to three seconds). In this manner, the three types of workload estimates are created using functions that weight the values assigned to the inequalities over a specified time span. The resulting instantaneous workload estimate 110, intermediate workload estimate 112 and overall workload estimate 114 are then output from the driving workload estimator 102. The output can include transmission to a specified location and logging to a specified location.

[0022] The disclosed invention provides the ability to estimate the workload that a driver is experiencing using data that is already available within a vehicle. Vehicle data, environment data and current task data can be used to create inferences about the driver's current state (i.e., instantaneous workload estimate), short term state (i.e., intermediate workload estimate) and long term state (i.e., overall workload estimate). The workload estimates can be utilized by display functions and controls within the vehicle to determine the timing of particular messages and when to enable or disable particular functions. For example, a message to rotate the tires can be presented to the operator of the vehicle when the workload estimate is on the low side and the operator is more likely to be able to process the information. Having three time spans for the workload estimates provides the ability to track the longer term effects of particular workload estimate elements. The ability to predict the driving workload simultaneously for different time spans can lead to better estimates of the driving conditions and driver's state, resulting in better communication between driver and vehicle. Additionally, this informed interface may potentially result in higher driver satisfaction with the vehicle and/or safer vehicle operation.

[0023] As described above, the embodiments of the invention may be embodied in the form of computer-implemented processes and apparatuses for practicing those processes. Embodiments of the invention may also be embodied in the form of computer program code containing instructions embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, or any other computer-readable storage medium, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the invention. An embodiment of the present invention can also be embodied in the form of computer program code, for example, whether stored in a storage medium, loaded into and/or executed by a computer, or transmitted over some transmission medium, such as over electrical wiring or cabling, through fiber optics, or via electromagnetic radiation, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the invention. When implemented on a general-purpose microprocessor, the computer program code segments configure the microprocessor to create specific logic circuits.

[0024] While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another.