Sunday, March 25, 2012

PL 13/12: Traffic study of Tromsø Public Library

Filed under: statistics — plinius @ 6:03 pm

Librarians have, in general, very little systematic information about activities inside their libraries.

Count The Traffic (CTT) is a cheap and simple method to gather such data. It gives a good numerical picture of how library users actually use the various parts of the library. CTT reveals both the quality – or the kinds of activity – and the quantity of use. Combined with data on the number of visitors it will also indicate the average length of stay.

The study presented below is the first of its kind in the county of Troms. I am happy to report that it was initiated by a “graduate” from our three week statistical training workshop Statistics in Practice (SIP): Tanmayo Olsen, from Troms County Library. SIP itself was financed by a grant from ABM-utvikling – and directed by Jannicke Røgler from Buskerud County Library and myself.

Tours of observation

CTT is based on regular “tours of observation” through the public areas of the library, normally once an hour, during one or two weekly cycles. Data gathering and analysis can be carried out by the library’s own staff rather than by hired observers and consultants.

To carry out a CTT, you need:

  • A time plan, with dates and times for all observation rounds (”sweeps”)
  • A floor plan covering all the public areas of the library
  • The plan should be divided into functional zones: reception area, newspaper section, children’s books, etc.
  • A list of activities to be observed
  • We recommend using – or adapting – the standardized CTT list (revised March 2012)

Getting started

You can test out the method for yourself in a couple of hours by

  • sketching a floor plan with zones
  • making one copy of the list of activities for each zone
  • doing a single tour of observation, noting the number of people engaged in different observable activities as you pass.
  • putting the numbers in a spreadsheet
  • finding the distribution of users by zone
  • finding the distribution of users by activity

A model study

A full scale CTT study should cover at least one – and preferably two – full weeks. If you want reliable quantititative data, the counting days should be spread out as much as possible. The ideal sampling plan would be one day a month through one full year. A decent alternative, however, is to

  • do a one week study (in a typical, routine, ordinary week)
  • register the number of visits on monthly, a weekly or even a daily basis for a year
  • repat the one week study a year later

The total traffic will probably vary quite a bit through the year. By counting the number of visits on a regular basis, you get data on these fluctuations. The actual usage pattern – how traffic and activities are distributed between zones – is likely to be more stable.
Comparing the first and the second CTT study will give a good idea of the actual pattern of usage and its degree of stability.

Tromsø, with about seventy thousand inhabitants, is the biggest Norwegian city north of the Polar Circle (See the entry on Tromsø in Wikipedia). The city built an impressive new central library a few years ago. In November 2011 the library carried out a one week CTT study.

Below we present the main findings. The full data set is available as a Google Docs spreadsheet at Traffic. Tromsø bibliotek. November 2011..



Tromsø traffic study

Usage during the day

The traffic is low in the morning, high in the middle of the day and moderate in the late afternoon. There are two pronounced “dips”, after 12 AM and after 2 PM. The dip at noon may reflect lunch.

The basic traffic data were:

  • The average number of visitors: 113 persons
  • The average duration of a library visit: 36 minutes

Opening hours and observation rounds

In 2011 the opening hours were:

  • Monday through Thursday: 9 AM – 7 PM
  • Friday: 9 AM – 5 PM
  • Saturday: 11 AM – 3 PM
  • Sunday: 12 AM – 4 PM

Since this is a large library, observations were carried out every other hour (rather than once an hour):

  • Monday through Thursday at 10 AM, 12 AM, 2 PM, 4 PM and 6 PM
  • Friday at 10 AM, 12 AM, 2 PM, and 4 PM.
  • Saturday at 12 AM and 2 PM,
  • Sunday at 1 PM and 3 PM

A total of 28 observation rounds were carried out, resulting in 3163 separate observations (instances of activity)

Usage during the week

When we look at the weekly pattern we must remember the differences in opening hours.

  • From Monday through Thursday the library is open from 9 AM till 7 PM. Traffic (dark green) increases from Monday through Wednesday, but goes down on Thursday.
  • On Fridays, the library is open from 9 AM tilL 5 PM. In order to compare like with like, we look at the number of persons present – on the average – during this period (middle green). The decline on Thursday is temporary. Friday is almost as busy as Wednesday.
  • On Saturdays, the library is open from 11 AM till 3 PM. For these hours, the light green line shows the samme pattern as before: increase from Monday through Wednesday, decline on Thursday, big increase on Friday – and the same high level on Saturday.
  • On Sundays, the library is open from 12 AM till 4 PM. During this part of the day, Wednesday and Friday have the highest traffic (blue line).

The average length of stay was

  • about 36 minutes on Monday through Thursday
  • about 30 minutes on Friday and Saturday
  • about fifty minuutes on Sunday

Three main activities

Users spend about four percent of their time in contact with staff, about one percent waiting for staff (or in other queues), and about two percent on activities that are not specified in our list of activities. Half the staff contact time occurs in the class room.

The remaining 93 percent of the observations fall into three broad categories:

  • standing or walking around
  • sitting down – with or without media (excluding computers)
  • sitting down with (active) computers

The three main activities can be carried out alone or in groups.

Clearly, individual users have a higher tendency to use computers.

Six activities

The standard list of activties divides each of the main activities into two subgroups. The next diagram shows the differences between individuals and groups with respect to these six activities:

  • Sits with stationary (library) PC
  • Sits with portable PC (lap top)
  • Sits with other media
  • Sits without using media
  • Browsing (walking while looking at media)
  • Standing or walking without using media

We see that the relative importance of groups increases as we go

  1. from stationary to portable PCs
  2. from PC use to interacting with other media
  3. from interaction with media to “non-interaction”

The trends look reasonable – once we have the data at hand. But I suspect computers are becoming more social with time.

Note that the revised standard list, from March 2012, makes a distinction between individual and group contact with staff, but this has not yet been implemented.

Activities hour by hour

The pattern of activities changes somewhat during the day. The bar diagram below makes it possible to study these changes.

Notable changes during the day include:

  • a dip in individual use of library PCs at noon – see ALPC
  • a peak in groups using media around 2 PM – see GRMD
  • a decline in collective standing or walking through the day – see GRUP
  • a decline in group browsing through the day – see GRBR
  • a peak in groups (just) sitting at noon, followed by a dip at 2 PM – see GRSI
  • an increase in contact with staff through the day – see STAF
  • an increase in queuing through the day – see QUE

Usage by area

The pie diagram reveals how much of the users’ time at the library was spent in different functional areas (zones).

About sixty percent of the users’ time was spent in the three main sitting areas:

  • work places (chair + table) without library computers (light green)
  • other types of seating (middle green)
  • work places (chair + table) with library computers (dark green)

Nearly one quarter of the time was spent in areas designed for standing or walking:

  • open space – which includes open floor space, corridors, stairs, elevators and toilet areas
  • shelf areas

In Tromsø, 84% of total usage in November 2011 occurred in these five areas.

Five floors

The library is big. The public has access to five floors:

  • Basement (Plan U)
  • Ground floor (Plan 0)
  • First floor (Plan 1)
  • Second floor (Plan 2)
  • Third floor (Plan 3)

The distribution of zones between floors is given in the table below. In our analysis we have combined observations from similar zones on different floors. The original data makes it possible to do a floor by floor analysis as well, however.

English and Norwegian terms

  1. PC seats (arbeidsbord med PC)
  2. Work places w/o PC (arbeidsbord uten PC)
  3. Informal seating (sitteplasser)
  4. Shelves (hyller)
  5. Service desk (skranke)
  6. Walking area (gangareal)
  7. Stairs (trapp)
  8. Lift/Toilets (heis/toaletter)
  9. Automats – lending and return (utlån- og innleveringsautomater)
  10. Group room (grupperom)
  11. Class room (undervisningsrom)
  12. Local collection/Arctic (lokalhistorie/arctic)
  13. Gaming (TV-/dataspill)
  14. Fairy tale area (eventyrrom)
  15. Play tables (lekebord)

We have defined:

  • Open space = Walking area + Stairs + Lift/Toilets

The diagrams below show the pattern of use in the five areas with most traffic:

Work places without computers

Work places have chairs with tables. Individuals use this space for

  • working with ordinary media (56% of the time spent in this zone)
  • using their lap tops (39%)

Groups also use this space for just talking:

  • working with ordinary media (46%)
  • using lap tops together (32%)
  • sitting together without using media (21%)

Informal seating

Individuals mainly use this space

  • to read (other media, 77% of the time spent)
Groups spend more time talking:
  • sitting together without using media (55%)
  • working with ordinary media (34%)

Work places with computers

The dedicated PC areas are totally dominated by individual and collective use of stationary PCs

  • individual use of library PCs (96% of time spent)
  • group use of library PCs (93%)

Open space

The open spaces are equally dominated by people and groups standing or moving around:

  • individuals who stand or walk without looking at media (98% of time spent)
  • groups that stand or walk without looking at media (92%)

Shelf areas and browsing

People and groups who enter the shelf areas are, of course, mainly looking at books and other media:

  • individual browsing (88% of time spent in the zone)
  • group browsing (89%)

The amount of browsing beyond the shelves is very limited:

  • Browsing in shelf area: 232 observations = 91% of all browsing
  • Total browsing: 256 observations = 9% of all time spent at the library (excluding STAF, QUE and ETC)

It is worth noting that collective rather than individual browsing is fairly common

  • Browsing in groups in shelf area: 86 observations = 37%
  • Total browsing in groups: 93 observations = 36%


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