How much are city parks worth if we never pay to enter them? A new study points to an unexpected answer: our phones already know.
Key points
· Researchers used anonymous mobile phone data
to estimate how much people value two popular green spaces in Singapore.
· Jurong Lake Gardens generated an
estimated S$54.7–S$66.8 million in annual recreational benefits, while Bukit
Timah (an urban protected area) generated S$6.95–S$9.07 million.
· Phone data can avoid memory bias, track
changes over time, count visitors more completely, and do it all cost-efficiently—though
there are real limits to what the data can show.
The hidden economy of free parks
Parks are free at the gate, but they’re not free to
build, maintain, or protect. So how do we put a number on the joy, exercise,
and mental calm they provide?
Economists often use the travel cost method—a
simple idea: the time and money people spend getting to a park (bus fares,
petrol, time) reveal how much they value the visit. Traditionally, we learn
this from surveys. But surveys are expensive, slow, and sometimes fuzzy
(humans forget!).
This study asks: What if we used big data instead?
A big-data twist: using mobile phone records
The researchers analyzed anonymous, aggregated mobile
phone counts—essentially how many devices traveled from different parts of
the city to each park—over June–December 2017. They then applied the zonal
travel cost method, which looks at visit rates from different neighborhoods
and translates travel effort into consumer surplus (think: benefit
beyond what you “paid” in time and transport).
Two test sites
· Jurong Lake Gardens — a
recreation-oriented urban park.
· Bukit Timah — a biodiversity-rich protected
area whose mission isn’t recreation first.
What they found
· Total visits (6 months): 1,469,830
across the two sites.
· Annual recreational benefits:
o Jurong
Lake Gardens: S$54,698,761–S$66,805,454
o Bukit
Timah: S$6,947,974–S$9,068,027
· Benefit per visit (consumer surplus):
o Jurong
Lake Gardens: about S$15.41 per visit
o Bukit
Timah: about S$2.18 per visit
These differences make sense: Jurong Lake Gardens is
managed to maximize everyday recreation; Bukit Timah is managed to protect
nature first. Importantly, benefits were spread across the island,
reflecting Singapore’s excellent public transport—value isn’t confined to
nearby neighborhoods.
Why mobile phone data helps
1) Fewer random errors
Phone data capture vast numbers of visits across the city, not just a small
survey sample.
2) No memory bias
No one has to recall last month’s trip—phones log visits as they happen.
3) Better coverage
Multiple entrances? Weekend surges? Phone data can see them, including
flows that on-site surveys might miss.
4) Lower cost at scale
Monitoring big areas over long periods becomes practical, which means we can
track trends—before/after a renovation, seasonal shifts, or even
heat-wave impacts.
…and where it falls short
· Less flexible modeling: Because the data
come as counts, you can’t analyze individual visitor traits or run the
more advanced individual/multi-site travel cost models.
· Boundary issues: If park borders don’t
align with how the phone data are packaged (e.g., by subzones), analysis gets
tricky.
· Privacy thresholds: To protect users,
very small counts are suppressed—which can hide lightly visited pockets.
· Coverage gaps: People without phones—or
who don’t use them during visits—won’t appear, likely making estimates conservative.
· Inconsistent access/formats: Different
telecoms share data in different ways; long-term monitoring depends on stable,
transparent data pipelines.
Why this matters for cities
Putting credible numbers on recreational ecosystem
services helps planners and the public do three important things:
1. See the invisible value
When development choices loom, it’s easier to defend green space if you can
say, “This park delivers tens of millions in annual public benefits.”
2. Target investments
Track which improvements (new trails, shade, water features) actually raise
benefits—and for whom.
3. Plan for resilience
Always-on data can reveal how heat, storms, or policy changes affect urban
nature use, helping cities adapt smarter.
Bottom line
This study shows that big data can sharpen a classic
environmental tool. By pairing mobile phone records with the travel cost
method, we can measure the real-world benefits of parks with greater confidence
and speed. That means better decisions, better parks, and healthier, happier
cities.
Original article: Jaung, W., & Carrasco, L. R. (2020). Travel cost analysis of an urban protected area and parks in Singapore: a mobile phone data application. Journal of Environmental Management. 261, 110238. https://doi.org/10.1016/j.jenvman.2020.110238