Automatic driving systems not only for cars, but also for wheelchairs are being developed. Improving the operability and safety of electric wheelchairs is an important issue. For example, if a driving system changes the speed of the vehicle without a driver's operation, it makes the driver uneasy. We developed a system to address this uneasiness. Our system, called the MIZUSAKI system, notifies drivers of a change in the speed gain, which is controlled by the system, before the change. This system uses 4 in-screen effects, which are intended to be seen in the peripheral vision and do not inhibit drivers' attention to driving. In developing this system, we have always considered the notification timing to be a key factor. We tested this system to find the best notification timing and found that if the anticipatory timing is 3 seconds before the speed gain changes or later.