Over the last year or so, advanced driver-assistance systems have been involved in crashes, according to a US Department of Transportation report. 70 percent of the incidents were caused by the advanced features of the car. The report may raise more questions than it answers because of blind spots in the data.

The report looked at systems that promise to take some of the tedious or dangerous bits out of driving by automatically changing lanes, staying within lane lines, braking before crashes, slowing down before big curves in the road, and, in some cases, operating on highways without driver intervention. Nissan's ProPilot Assist is one of the systems included in the system. There is still a lot to learn about how a new breed of safety features work on the road.

The federal government has wildly different ways of receiving crash data from the automotive industry. After a crash, some companies, like GM, can pull data from their cars. They are able to quickly comply with the requirement. Toyota and Honda aren't the only ones that don't have these capabilities Chris Martin, a spokesman for American Honda, said in a statement that the company's reports to the DOT are based on "unverified customer statements." Only with the permission of the customer or law enforcement can the car maker pull the data from its vehicles.

Only 60 percent of the crash reports came through the car's systems. 40 percent were through reports from customers, claims, and media. The report doesn't allow anyone to makeapples-to-apples comparisons between safety features.

The data the government collects isn't put in full context. The government doesn't know how many crashes an advanced assistance feature causes. Some incidents may appear more than once in the data set according to the National Highway Traffic Safety Administration. Because they have more cars on the road, automakers with high market share and good reporting systems are more likely to be involved in crashes.

The chair of the National Transportation Safety Board says it's important that the NHTSA report doesn't discourage automakers from providing more comprehensive data. She said that the last thing they want is to penalize manufacturers. Data that tells us what needs to be done to improve safety is what we want.

Without that transparency, it can be hard for drivers to compare and use features in their car, and for regulators to know who is doing what. As we gather more data, NHTSA will be able to identify any emerging risks or trends and learn more about how these technologies are performing in the real world.