AUSTIN (KXAN) -- A crash involving five semi-trucks and two cars early Tuesday morning near Round Rock snarled traffic for hours. It happened around midnight on southbound Interstate 35 near the Grand Avenue Parkway exit and happened in a construction zone. The Texas Department of Transportation (TxDOT) said on its website there were more than 26,000 traffic crashes in 2023 inside work zones. Move over, slow down: TxDOT pleads for people to drive safely through work zones The crash early Tuesday is a good reminder of how dangerous work zones can be. TxDOT estimates more than half of the state's population lives near the major interstate. The department said, right now, there are more than 3,400 active work zones across the state. KXAN dug through TxDOT data to see where the deadliest crashes are most likely to occur. Most are near major cities off I-35, like Austin, San Antonio or Dallas. The most recent data from 2014 to 2023 showed there have been 15 deadly crashes in Hays County, 82 in Travis County and 21 in Williamson County during that time period. In fact, TxDOT said nearly 5% of traffic deaths statewide happened in a work zone. The same data showed work zone deaths are trending up since 2018. TxDOT said the biggest problem is drivers are driving too fast, not paying attention and -- many times -- tailgating. It also blamed people making illegal lane changes when there's a solid white line. Which Texas roads have the most traffic fatalities? The North American Transportation Management Institute said semi drivers are also required to go through advanced training annually, which includes everything from hazardous materials to safety and Department of Transportation compliance. As a reminder, it is state law that you must move over for law enforcement personnel, first responders and road maintenance crews. There are strict penalties that now include fines up to $4,000 or even jail time.