SIOUX CITY | A first sign could be the car drifts -- first right, then weaving back left, a few feet at a time, perhaps off pavement and onto the shoulder.
If you get close enough to the driver, you also might see his or her eyes, cast downward, rather than on the highway.
Officials say those are indications people in vehicles have their attention on mobile devices, texting or checking social media.
"It is obvious in people's driving habits," Iowa State Patrol Trooper John Farley said.
He and others see it frequently, but often can't issue tickets, since the drivers aren't breaking any other Iowa law.
That could change: The Iowa Legislature is considering strengthening public safety by passing new laws on what people can't do when driving.
Farley has taught about 10 defensive driving classes this winter. He asked people how often they believe others on the roads beside them use devices while driving. Farley figured the response would be about 50 percent.
"Every group that I talked to, consistently, said 80 percent or above," Farley said. "That tells me people are recognizing it is a problem."
Richard Padilla, 52, of Scottsbluff, Nebraska, said he has an iPhone but does not give into temptation to text while driving. Speaking during a Sioux City stop, Padilla said texting while in a car is becoming accepted, similar to how people when he was young would make the poor decision to drink alcohol and drive.
"It is generational," Padilla said.
Farley and South Sioux City Police Chief Ed Mahon said people of various ages delude themselves and overlook reasons why they should not use devices on the highway. Farley said young people don't have enough experience to realize they should give full attention to the road, while older people think they are accomplished drivers and can pull off some usage while behind the wheel.
The Iowa State Sheriffs & Deputies Association has aired data for legislators related to traffic mishaps involving individuals ruled to be distracted by a phone or other electronic device. Those crashes nearly doubled from 659 in 2010 to 1,100 in 2015, while fatalities increased from four to 14 during the same period.
The National Safety Council says more than one in four vehicle crashes involve cell phone use at the time of the incident. The council also says it is difficult to have accurate statistics, since law enforcement workers often only can determine if a cell phone was being used in the time of a collision after the fact, half the time through an admission by the driver.
However, sometimes authorities can get a definitive case by videotaping drivers from their patrol cars. Farley pulled beside a teen driver at a stop light on a busy Sioux City primary street. The girl had her eyes on her device, her hands moving.
"I am watching her text. I hit my camera, I hit record," Farley said. He pulled her over a few seconds later.
"She immediately said, 'I wasn't texting.' Flat-out denial," Farley recounted.
Differing rules in three states
Siouxlanders who want to use a mobile device or smart phone in their car need to be aware of varying laws, depending upon whether they are driving in Iowa, Nebraska and South Dakota. Iowa has the most stringent rules.
The Iowa Legislature is considering banning hand-held use of phones by drivers. On Wednesday, a senate committee took up a measure to make texting while driving a primary offense – a move that backers believe will help reduce the incidence of distracted driving on roadways.
But for now, the Iowa law for adult drivers specifies that texting while driving is prohibited, but it is a secondary offense, which means law enforcement cannot stop a driver solely for texting.
"If we see somebody who is obviously texting, but (he or she has a) seat belt on or isn't speeding, we can't do anything about it," Farley said. "The law needs to be more evenly enforceable."
Farley favors a wide ban of all hand-held devices used by drivers. He noted people in cars may not just be using a phone but perhaps a tablet computer.
Under current law, an adult driver may use a hand-held phone to search for contact information, select music, type addresses into a navigation system or play games.
But the rules for Iowa teen drivers, who are going up the learning curve, is different, Farley noted. Iowa teens are prohibited from using hand-held electronic devices.
For now, 15 states prohibit drivers’ use of hand-held phones.
In South Dakota, there is no state law that specifies that people can't talk on the phone while driving. As in Iowa, South Dakota law specifies that texting while driving is a secondary offense, so officers have to see another broken driving law to stop and ticket the driver, South Dakota Department of Public Safety Public Information Officer Tony Mangan said.
There are a few cities in South Dakota, such as Sioux Falls, where a local ordinance makes texting while driving a primary offense and people can be pulled over.
Mangan said he didn't have a feeling for whether South Dakotans want tougher laws regarding mobile devices.
"Pay attention when you are driving. That is what you are supposed to be doing," Mangan said.
South Sioux's Mahon said there are no Nebraska laws saying adults can't use phones to make calls or text while driving. But texting is not allowed by teen drivers, similar to Iowa.
Mahon said people who text while driving can be slow to react when stoplights move from red to green. He said some of the signs used to remind him of drunk driving, yet today they are tied to those using mobile devices.
Mahon isn't calling on legislators to enact tougher laws, but added he wouldn't be against them if Nebraska lawmakers did.
"It is a safety message, nothing more," Mahon said. "If you are driving, drive. If you have other things, do them later."