A Speeding Handrail?

Q: On escalators, why does the handrail move faster than the stairs? It defies logic.
Dan, Southampton, England

A: When I first read this question, I paused and tried to remember. Yes, it did seem like my hand went faster than my feet the last time I rode an escalator, but I wasn't sure.

So, one fine spring afternoon recently, I hopped in my red 4Runner, and headed north to the nearest big shopping mall: Cottonwood. I rode six escalators, all that Cottonwood had. Boarding each one, I clamped my elbow to my side (like I was holding a newspaper there) and reached for the handrail as I stepped on the moving stairs. My hand kept pace with the rest of my body. It did not tug me forward (moving faster) or push me backwards (moving slower). I concluded handrails do a good job of keeping even with the stairs.

How the handrail works:

The escalator drive shaft (which drives the stairs) also drives the handrail belts through a gear wheel and chain system. So the handrail system is closely, but not directly, coupled to the stair-drive system. Therefore, it's possible for a moving handrail not to keep exact pace with its moving stairs. However, all the escalators I rode that day had well-synchronized handrails.

I checked with the American Society of Mechanical Engineers about escalator handrail safety codes. "Though I cannot comment on a manufacturer's particular design," Geraldine Burdeshaw emailed, the code "does require the handrail to be substantially the same speed as the steps." I've included the pertinent safety code below.

Trivia

The longest single-span uninterrupted escalator in Europe is in the Moscow Metro; it is 413-feet (126-m) long, and takes nearly 3 minutes to ride.
In the Western Hemisphere, the longest is in the Washington DC metro: 230-feet (70-m) long.
Jesse Reno patented the moving stairs in 1892 and, four years later, created a 6-foot escalator 'ride' on Coney Island in New York City.

Further Reading:

Escalator information, Otis Elevator Company
Magic stairways, University of Houston
The Way Things Work: An Illustrated Encyclopedia of Technology, C. van Amerongen, 1967.

Readers' answers:

That [a faster handrail] is not really possible because, if you were holding onto a handrail that was moving faster, you would lean over gripping the handrail until you relaxed your grip or fell off the step. You never hear stories of people falling off escalators. Another reason is that the stairs and the railing belt are running off of the same drive wheel so there is no way the handrail could be faster.
Josh, Stow, Ohio, USA

Escalator steps are driven by an electric motor. The steps drive is connected to the handrail drive by a drive belt. Over time, that belt can get a bit stretched out. Without maintenance, it will eventually break. This is why all escalators come equipped with handrail sensors. Ultimately, it's a maintenance issue.
LdySaphyre, Gainesville, Florida, USA

The handrail on the escalator moves faster than the stairs to motivate the user to walk up the escalator and not just ride. If everyone walked up, even slowly, this would allow more people to use the escalator, and satisfy the person behind you who wants to get up the escalator faster.
Nick, Maysville, Missouri, USA

From the ASME A17.1 Safety Code for Elevators and Escalators (2004 edition):

6.1.3.4.1 Type Required. Each balustrade shall be provided with a handrail moving in the same direction and at substantially the same speed as the steps. In the case of curved escalators, this shall be substantially the same angular velocity. The speed of the handrail shall not change when a retarding force of 450 N (100 lbf) is applied to the handrail opposite to the direction of travel.

(Answered April 9, 2007)