Module 1, lesson 4 · 30 minutes
Levels of Service: what each band feels like
J. J. Fruin graded pedestrian spaces from A to F by how much room each person has. The same density earns a different letter in a corridor, on a stair and in a queue.
You’ll be able to
- recall Fruin’s A–F bands for walkways, stairways and queuing areas;
- translate a described scene into a band;
- explain why queuing bands tolerate far higher density than walkway bands.
Introduction
Picture two crowds at 1.5 p/m². One is walking along a station concourse at rush hour: people are slowed, overtaking is out of the question, and the corridor is carrying close to all it can. The other is standing in a queue for a lift: people have a little room around them and nobody is bothered.
Same density, very different experiences. Fruin’s Levels of Service capture exactly that difference. The concourse is graded E, one step from breakdown. The queue is graded D, ordinary and tolerable. This lesson is about why, and about using the letters well.
Grading the experience
J. J. Fruin’s book Pedestrian Planning and Design (1971; revised 1987) gave planners a way to grade a pedestrian space by the experience it offers.
The logic of the letters runs the same way in every table. A to C are comfortable: people choose their own speed and position. D is restricted: you notice others and adjust to them. E is the capacity band: the space is carrying about as much as it can. F is breakdown: movement becomes erratic, stop-and-start, or impossible.
Fruin wrote in square feet per person. The metric tables below, from the US Federal Highway Administration and Transit Cooperative Research Program reproductions, give space per person in m², and we add density, because Still recommends always thinking in people per square metre
Walkways
Walkway bands grade a moving crowd by space per person and by the flow per metre of width it carries
| LoS | m²/person | p/m² | p/m/min | Imperial | Feels like |
|---|---|---|---|---|---|
| A | ≥ 3.2 | ≤ 0.31 | ≤ 23 | ≥ 35; ≤ 7 | Walk where you like at your own speed. |
| B | 2.3–3.2 | 0.31–0.43 | 23–33 | 25–35; 7–10 | Others are noticeable; you still walk freely. |
| C | 1.4–2.3 | 0.43–0.71 | 33–49 | 15–25; 10–15 | Normal pace, but overtaking and crossing take care. |
| D | 0.9–1.4 | 0.71–1.1 | 49–66 | 10–15; 15–20 | Speed and passing restricted; you adjust constantly. Walking speed falls to about 1.0 m/s. |
| E | 0.5–0.9 | 1.1–2.0 | 66–82 | 5–10; 20–25 | Everyone slowed, to roughly 0.6–1.0 m/s; the walkway is at capacity. |
| F | < 0.5 | > 2.0 | variable | ≤ 5 | Shuffling and stopping; flow breaks down. |
Two cross-checks make these bands easier to trust. First, Weidmann’s curve, derived independently, gives flows at the band edges of about 25, 34, 52, 66 and 73 p/m/min, close to Fruin’s 23, 33, 49, 66 and 82 (our arithmetic
A worked example
A corridor 3 m wide carries 120 people a minute. What Level of Service is it?
- Flow per metre of width: 120 ÷ 3 = 40 p/m/min.
- In the walkway table, 40 p/m/min lies in 33–49: LoS C.
- Check with density. 40 p/m/min is 0.67 p/m/s. On the free-flow branch of Weidmann’s curve that needs about 0.52 p/m², walking at about 1.29 m/s (our arithmetic). 0.52 p/m² is also in band C. The two columns agree.
The density check matters. A flow of 40 p/m/min could also come from a dense crowd on the congested branch (lesson 3). If a camera shows that crowd at 4 p/m², the corridor is at F, not C, however steady the count looks.
Stairways
On stairs, each person needs more length for their stride, and overtaking is hard. The stairway bands, attributed to Fruin’s 1987 edition, are given in space per person and flow
| LoS | m²/person | p/m² (approx.) | p/m/min | Feels like |
|---|---|---|---|---|
| A | ≥ 1.9 | ≤ 0.53 | ≤ 16.4 | Climb at your own pace. |
| B | 1.4–1.9 | 0.53–0.71 | 16.4–23.0 | Own pace, with occasional adjustments. |
| C | 0.9–1.4 | 0.71–1.1 | 23.0–32.8 | Pace set partly by the person in front. |
| D | 0.7–0.9 | 1.1–1.4 | 32.8–42.6 | Pace set by the crowd; no passing. |
| E | 0.4–0.7 | 1.4–2.5 | 42.6–55.8 | Step by step behind the person in front; at capacity. |
| F | ≤ 0.4 | ≥ 2.5 | — | Stop-and-start; flow breaks down. |
The capacity band on stairs, about 43–56 p/m/min, is well below the walkway’s 66–82. The Green Guide makes the same distinction with its two rates of passage, 82 p/m/min on level surfaces and 66 on stepped ones
Queuing and standing areas
In a queue, or anywhere people stand and wait, nobody needs room to walk. The bands are about personal space, and about whether you can move about within the crowd
| LoS | m²/person | p/m² | Feels like |
|---|---|---|---|
| A | ≥ 1.2 | ≤ 0.8 | Stand and move about freely without disturbing anyone. |
| B | 0.9–1.2 | 0.8–1.1 | Some movement without disturbing others. |
| C | 0.7–0.9 | 1.1–1.4 | Moving about means asking people to make way. |
| D | 0.3–0.7 | 1.4–3.3 | You can stand without touching anyone; moving through means contact. |
| E | 0.2–0.3 | 3.3–5 | Contact is unavoidable; moving through the crowd is barely possible. |
| F | ≤ 0.2 | ≥ 5 | Bodies pressed together; no movement. |
The “feels like” lines follow from the geometry of lesson 1. A clothed body occupies about 0.15 m² of floor
Why standing crowds are graded so differently
Walking needs space in front of you: a stride, a margin for the person ahead to slow down, room to step round someone. Standing needs only the space you occupy plus a little personal room. So a density that has already broken a corridor’s flow (walkway F, above 2 p/m²) still leaves a standing crowd in D. The queuing bands are not more forgiving because standing is safe at any density. They are measuring a different thing.
This is also why the Green Guide’s 4.7 p/m² for standing spectators
Fruin’s letters grade how a space feels and how well it flows. They are not crush thresholds. A walkway at F is failing as a walkway but is not necessarily dangerous; a queue at E may be tolerable for minutes and harmful for hours. The densities at which crowds start to hurt people, and their sources, are the subject of Module 2.
From a scene to a band
To grade a real space, work through three questions.
- Moving or standing? A concourse, ramp or corridor is a walkway. A stair is a stairway. A queue, a pen, a viewing area or a platform where people wait is a queuing area.
- What can you measure? For a moving crowd, a count over a line of known width gives flow per metre. For any crowd, a head count in a known area gives density (lesson 1).
- Do the columns agree? If the flow says C and the density says F, the crowd is on the congested branch, and the density is the one to believe.
A 4 m wide stair carries 200 people a minute down from a stand. What is its Level of Service? Would the same flow on a 4 m level walkway get the same letter?
200 ÷ 4 = 50 p/m/min. On the stairway table that is in 42.6–55.8: LoS E, at capacity. On a walkway, 50 p/m/min falls in 49–66: LoS D. The same flow is harder work on a stair, which is why stair capacities and the Green Guide’s stepped rate are lower.
A pen in front of a stage measures 10 m by 20 m and holds about 600 people, standing. What band is that, and what is it like to be in it?
600 ÷ 200 m² = 3 p/m², or 0.33 m² each. In the queuing table that is D (1.4–3.3 p/m²), near its upper edge: you can stand without touching anyone, but getting through the crowd means contact. It is below the Green Guide’s standing maximum of 4.7. Remember it is an average: the patch nearest the stage is likely to be denser (lesson 1).
- “A density has one Level of Service.” The letter depends on the context: 1.5 p/m² is walkway E, stairway E and queuing D.
- “LoS F means people are in danger.” F means the space has stopped working as intended. Danger thresholds are a separate question, covered in Module 2.
- “The Green Guide’s 4.7 p/m² is a walkway figure.” It is a standing figure and sits in queuing E. On a walkway it would be far into F.
- “Flow alone tells you the band.” The same flow occurs on both branches of the fundamental diagram. Check density too.