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Interview Question

Analyst Interview

How many traffic lights in Manhattan?

Tags:
case, guesstimate
Answer

Interview Answer

12 Answers

0

1 in base (Traffic Lights in Manhattan)

Sure, it's cheating, but the question is absurd. Ask a silly question, get a silly answer.

FrankieAvocado on 30-Dec-2010
2

3. Red, Yellow and Green

Darknavigator on 31-Dec-2010
2

Let X be the number of blocks west to east.
Let Y be the number of blocks south to north.
   then X * Y = the number of traffic lights.

Ed C on 31-Dec-2010
0

0, they use traffic cops!

nb on 04-Jan-2011
1

Q: How many traffic signals are there in New York City?
A: As of January 2006, there were 11,871 signalized intersections Citywide, including 2,795 in Manhattan, 4,100 in Brooklyn, 2,942 in Queens, 1,536 in the Bronx, and 500 in Staten Island.

http://www.nyc.gov/html/dot/html/faqs/faqs_signals.shtml

BobD on 06-Jan-2011
1

Q: How many traffic signals are there in New York City?
A: Not enough, traffic there is terrible.

Matthew on 10-Jan-2011
2

Sounds like your standard estimation problem, along the lines of: how many basketballs will fit in this room, how many piano tuners are there in America, and how many gas stations are there in America?

All designed to see how you come up with best guesses, how logical your thought patterns are, etc. (I've been asked the last two - I must have done well, because I got the job).

Andrew on 11-Jan-2011
0

I had ballparked 225 blocks and 12 avenues...225*12=2700. googline the answer gave me:

A: As of January 2006, there were 11,871 signalized intersections Citywide, including 2,795 in Manhattan, 4,100 in Brooklyn, 2,942 in Queens, 1,536 in the Bronx, and 500 in Staten Island.

http://www.nyc.gov/html/dot/html/faqs/faqs_signals.shtml

so i was pretty close!

Matt on 11-Jan-2011
1

I got the similar one "How many registered cars are there in your town?" Obviously not knowing, I went about it like so:
1) Go to the DMV and find out .
2a) If that information isn't directly connected, I find out how many registered cars are there in my state, then took the names and cross-referenced them with people who live in my town.
2b) I also made sure to include that some people live in the county but live in-between towns. I find out what is considered "within city limits" and "not within city limits", and added those people within.
3) If that information isn't available, I estimate using (2b) above with "How many cars on average does a person register in Dayton", then multiplied, adding some +/-%.

May have over-analyzed, but I wanted to show how to get the direct answer, then what options you use when you don't have it.

Dave H on 11-Jan-2011
0

good probability that the answer includes a fraction due to boundary lines

chaos on 11-Jan-2011
0

As many as needed plus 10% because city government is involved.

leephil on 18-Jan-2011
1

Estimation problem:

There are about 250 streets north to south in Manhattan and 12 avenues east to west, but some discontinue because of the shape of the island and because of central park. Shave off to a closer estimation of 225 streets and 10 avenues. That gives us 2250 intersections. Almost all Manhattan streets are one way, so that gives us 2 directions the lights need to point, but it is standard to have two lights per direction which gives us 4 lights per intersection. My guess would have been 9000 traffic lights.

Seems from Matt's post my intersection guess wasnt that bad.

looking for a job on 28-Nov-2012

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