An estimated 27 men died during the construction of the Brooklyn Bridge; even more suffered health issues. Workers called "sandhogs," excavated the river beds to make room for caissons. They worked in extreme heat and pressure, often subject to the "bends," caused by resurfacing to normal atmospheric pressure too quickly—symptoms included extreme muscle pain, cramping, vomiting, and slurred speech, among others. Digging was suspended after three men died. Engineers tried to minimize the human cost, but it was already present. Other laborers fell to their deaths or had pieces of the bridge fall on them. It is still not known the exact number of deaths resulting from the bridge's construction, as laborers who died as a result of their injuries later would not be counted. Even after its completion, on the day of the opening, a woman was killed when there was a sudden stampede. To this day, crowding is a major concern of the bridge. Though tourism—and therefore, pedestrian use—have increased, most of the width of the bridge is devoted to private transportation for cars. At its opening, the IRT (the precursor to the subway) occupied part of the bridge, but its function as part of public transit has nearly disappeared. Today, bike lanes have been completely eliminated, and the promenade is as narrow as ten feet in places. On busy days, as many as 25,000 pedestrians cross the bridge. Though the construction of the bridge was costly, today it is still an engineering marvel. At the time it was built, it was the longest bridge in the world and the first to use many of its design features. Its longevity demonstrates its strength, and it will continue to attract tourists for this reason.