The friendly folks at the Association of Health Care Journalists held a conference last week in San Antonio, and they invited me to present an introduction about Google Fusion Tables.

If you’re familiar with Microsoft Excel or Access, you might like Fusion Tables. It’s a free tool that allows you to create interactive maps and charts with data.

Related: Google Refine: A tool for journalists looking for great stories in data

For journalists, this is fantastic. Fusion Tables unlocks the data stuck in your hard drive and lets you easily share it with readers in a compelling format. Check out some great examples at Matt Stiles’ blog, the Daily Viz.

If you’re interested in learning more, check out this slideshow for a step-by-step tutorial about some of the basics.

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A few months ago, my boss, Express-News Projects Editor David Sheppard, asked me to see what we could find out about wrong-way crashes on highways. It seemed like there were a lot of these deadly accidents in the news lately, and local officials had recently unveiled a $500,000 pilot project to install flashing wrong-way signs and radar on a 15-mile segment of U.S. 281.

I wrapped up what I was working on and teamed up with reporter Vianna Davila, who covers transportation. We had to answer two deceptively simple questions. How often do wrong-way crashes happen? And how does Bexar County compare to other counties?

We turned to a giant database maintained by the Texas Department of Transportation called the Crash Records Information System. It’s derived from accident reports filled out by law enforcement officers, and it tracks hundreds of details about every accident in Texas — including wrong-way crashes.

But we soon learned there was no quick and easy way to filter the data for the specific wrong-way accidents we were looking for — crashes on major divided highways with exit and entrance ramps.

Related: Road rage in Texas: Find accidents in your neighborhood with this interactive map

The database had a “road type” field, with categories that included interstates, tollways and U.S. and state highways. So far, so good. But some state highways are actually busy roads, such as Bandera Road. The wrong-way crashes on those boulevards are different from the type of accident we were examining. We weren’t writing about distracted drivers who cross a center line into oncoming traffic. We were writing about drivers who head up exit ramps and into oncoming traffic on busy highways and interstates.

We ended up selecting the five Texas counties with the largest populations, mapped the wrong-way accidents with Google Fusion Tables, and then eyeballed each location to make sure it actually occurred on a major highway. Here’s how the finished product looked for Bexar County:

It took hours of work but the result was a set of specific crashes we were looking for. And the final numbers were surprising — Bexar County ranked high in wrong-way accidents for the years 2007-2011. It even had more crashes than Dallas County, which is more densely populated and has more traffic. To our knowledge, no one has done this kind of comparison in recent years.

If you work for a news organization and you’re jumping into data journalism (and you should be), it’s a good idea to share your methodology and findings with the government employees who oversee the data. You don’t want to be surprised by an error they catch after the story is published. And it gives the agency a chance to respond if your findings cast the agency in a harsh light.

It was certainly surprising to learn Bexar County ranked so high. The other surprise was how long the deadly problem flew under the radar. Despite several high-profile, deadly wrong-way crashes, local officials didn’t start talking about ways to prevent them until the summer of 2010.

To learn more, check out our two-part series about wrong-way crashes. And check back here when we see how the pilot program is working to stop wrong-way drivers.

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