Four-leg intersection
Stop or signal control · one lane each way
Compact roundabout
Single lane · entering traffic yields · counter-clockwise
Schematic plans: lane widths and turning paths are drawn for legibility, not to scale. Counts assume one lane on each approach and follow FHWA's Roundabouts: An Informational Guide (Exhibits 5-2, 5-5, 5-6). Pedestrian conflicts at the intersection use FHWA's signalized-intersection count: four per crosswalk.1
The type matters as much as the count
Red crossing conflicts are where right-angle and left-turn crashes happen, at whatever speed drivers arrive. A roundabout has none. Its merges and diverges happen at low speed and at shallow angles, which lowers the relative speed when a crash does happen.1
Follow a left turn above: the count only drops from 8 to 6, but 4 of the intersection's 8 are crossings.
Fewer fatal and injury crashes after converting an intersection to a roundabout. FHWA lists roundabouts as a Proven Safety Countermeasure.2
FHWA-SA-21-042, citing Highway Safety Manual crash modification factors.
Low speeds at a roundabout help people walking the most and people cycling the least. The Dutch answer is to take cyclists out of the ring and give them their own crossing, set back one car length from it. Compare three ways to handle bikes at the same compact roundabout.
Mixed traffic
Cyclists ride in the circulating lane with cars. At a compact roundabout cars move at close to bike speed, so a confident rider can hold the lane. Many European countries allow this on low-volume, low-speed single-lane roundabouts, and it remains a standard option at US single-lane roundabouts. It stops working as traffic and speeds rise, and on multilane roundabouts.1,5
Example trip, south to north: 4 conflicts, all merges and diverges with cars moving at about the cyclist's speed.
Flanders, 9 roundabouts: no significant change in injury crashes involving cyclists (index 0.91, 95% CI 0.45–1.84).3
Bike lane on the ring
A painted lane on the outer edge of the circulatory roadway. It puts cyclists where entering drivers are looking past them for a gap in car traffic, and where exiting drivers turn across them with the cyclist beside or behind. Most European countries avoid it, and England's active-travel guidance discourages it.1,9
Example trip, south to north: 4 conflicts, each where the driver is focused on car traffic or has the cyclist beside them.
Flanders, 40 roundabouts: injury crashes involving cyclists rose 93% after conversion (index 1.93, 95% CI 1.38–2.69). It was the only design with a statistically significant change.3
Separated cycle track
A one-way track circles the roundabout about 5 m outside the circulating lane. Drivers meet cyclists at one crossing per leg, close to a right angle, with the cyclist in front of them. An exiting driver who stops for a cyclist waits in that 5 m space without blocking the ring. An entering driver deals with the cyclist first and the ring second.6,7
Example trip, south to north: 2 conflicts, both on the east leg, at about 80° on this drawing.
Flanders, 38 roundabouts: no significant change (index 0.83, 95% CI 0.56–1.23). FHWA reports a 90% drop in injury crashes at Dutch roundabouts with separate cycle paths where cyclists did not have right of way.3,4
Inside built-up areas, Dutch practice gives cyclists priority at the crossings: red asphalt, block markings, and shark's teeth facing drivers.7
Outside built-up areas, cyclists yield: the shark's teeth face the cycle track and the crossing loses its red surface. Danish guidance puts rural bypass tracks 10–30 m from the ring (drawn here at 5 m for comparison). The large early Dutch gains were measured where cyclists yielded.4,6
Cyclist injury crashes after conversion, by bike facility
Flanders, Belgium: 90 roundabouts built 1994–2000. Effectiveness index (1 = no change relative to comparison sites), with 95% confidence interval, log scale.3
Hover a row for details. Only the cycle-lane interval sits wholly above 1.
What makes the Dutch layout work
In practice
Fendon Road, Cambridge, UK
The UK's first Dutch-style roundabout opened in 2020, with a circulating cycle track and crossings on every arm. Drivers gave way more often at the crossing with give-way triangles.10
Bend, Oregon
The city's 2024 design manual defines a "separated roundabout," with its own bicycle circulation lane, for key walking and biking routes.8
NCHRP Research Report 1043
The 2023 national Guide for Roundabouts adds separated bike lane designs around the full roundabout, drawing on European practice.5
Sources
- FHWA (2000). Roundabouts: An Informational Guide, FHWA-RD-00-067. Ch. 5: Exhibits 5-2 (32 vs. 8 vehicle conflicts), 5-5 and 5-6 (pedestrian conflicts), p. 121 (European bicycle practice). Ch. 1: Exhibit 1-7 and §1.6.3 (urban compact roundabouts).
- FHWA (2021). Proven Safety Countermeasures: Roundabouts, FHWA-SA-21-042, citing AASHTO Highway Safety Manual (2010) CMFs 211 and 226. FHWA Proven Safety Countermeasures.
- Daniels, S., Brijs, T., Nuyts, E., & Wets, G. (2009). Injury crashes with bicyclists at roundabouts: influence of some location characteristics and the design of cycle facilities. Journal of Safety Research, 40(2), 141–148. Table 10.
- Schoon, C., & van Minnen, J. (1993). Accidents on Roundabouts II, SWOV R-93-16; van Minnen, J. (1996), SWOV. Both as reported in FHWA (2000), Exhibit 5-16 and p. 121. Figures taken from FHWA's summary, not the SWOV originals.
- National Academies (2023). Guide for Roundabouts, NCHRP Research Report 1043; summarized in Pochowski, A., & Nan, R. (2024), New guidance paves the way for better bicyclist experiences at roundabouts, Kittelson & Associates.
- Andersen, T. (2019). Roundabouts in urban and rural areas, and mini-roundabouts. Cycling Embassy of Denmark.
- Siegel, R., Groot, T., & Andriesse, R. De rotonde van de toekomst. Goudappel (Dutch; cites CROW guidance on priority and cycle-track distance).
- City of Bend (2024). Roundabout Design Manual. §2.1.2 and Table 1 (compact roundabouts), §2.1.6 (separated roundabouts), §10.3.4 (splitter islands).
- Active Travel England. Introduction to roundabouts (refers to LTN 1/20, §10.7).
- Essex, S. (2024). Dutch Style Roundabouts Briefing Note. Transport Initiatives.
- U.S. Access Board (2023). Notable changes in the PROWAG final rule, R306.4.2.