TOKYO (Kyodo) -- Around 45 percent of self-employed delivery drivers working for the Japanese unit of Amazon.com Inc. said they had been involved in a traffic accident while on the job, a recent survey conducted by a labor union has shown.

The survey was organized by the General Support Union, which set up a division exclusively for self-employed Amazon drivers in January to negotiate higher wages and establish an appropriate limit on the number of deliveries assigned.

In the survey, carried out from January to Dec. 1, 71 out of 160 respondents said they had experienced some sort of traffic accident while making a delivery, such as colliding with another vehicle or an electricity pole.

The survey showed accidents were often caused by drivers rushing to deliver a parcel or limited visibility due to excessive packages. About 89 percent of respondents said reducing the number of packages would help prevent accidents.

Around 72 percent said they were assigned 21 to 30 packages for delivery per hour, with most describing the workload as "too much." Some respondents said they had "no time to go to the bathroom" and felt "it is not worth the pay."

Amazon Japan G.K. said the survey does not reflect the opinions of its tens of thousands of drivers across the country, claiming that it provides parcel allocations designed to ensure safe and comfortable deliveries, as well as 24-hour support.

"The safety of our drivers is our top priority," the firm said.