Continuity mistake: When Daryl is driving the hospital van, it shows that he is going to land upside down, on the vehicle's roof, when he drives off the parking garage. In the next scene, the vehicle lands on its wheels, as if it has done a complete front flip. (00:30:00)
Visible crew/equipment: You can see the casting directors on The Bridge behind Carol and Daryl wearing lime green vests. Then below The Bridge, you can see people driving their cars and a person walking in the parking lot. (00:26:57)
Answer: Walkers are attracted to noise, they can tell who's dead and who isn't dead, in S1 when Rick and Glenn cover themselves in walkers' guts they're able to get far by walking through the herd of walkers because they smell like they're dead, but as soon as the guts get washed off by the rain the walkers immediately attack them, if you draw attention to yourself they will attack you which we've seen that many times throughout the series that it's not always successful. Whether you're covered in guts hiding under dead corpses or under a car.