Safe following distance and stopping distance
Singapore's Highway Code following-distance guidance, SPF's three-second and motorcycle six-second rules, and its approximate stopping-distance chart.
Primary source: https://sso.agc.gov.sg/SL/RTA1961-R11?DocDate=20240301&ProvIds=pr67-%2Cpr69-&ViewType=Within&WiAl=1
The Highway Code says to allow at least one car length for every 16 km/h of speed so that you can adjust speed and stop within the space between your vehicle and the vehicle ahead (SSO, Highway Code r. 67).
The current SPF Basic Theory of Driving handbook also teaches the “Three-Second” Rule (previously the two-second rule): as the car ahead passes a stationary object, count “one-thousand-and-one, one-thousand-and-two, one-thousand-and-three”. If your vehicle reaches the same point before you finish counting, you are following too closely and should slow down. The handbook says this rule applies to all vehicle types at any speed (SPF, Basic Theory of Driving handbook, pp. 60–61).
The Highway Code says to watch the stop light on the car ahead and the traffic beyond it. The SPF handbook similarly says to watch the brake lights of the car immediately ahead and the traffic beyond that car (SSO, Highway Code r. 68; SPF, Basic Theory of Driving handbook, pp. 60–61).
The current SPF Basic Theory of Driving handbook calls this the three-second rule, explicitly noting that it was previously the two-second rule. Count three seconds after the vehicle ahead passes a stationary object; if your vehicle reaches the same spot before you finish, slow down because you are following too closely. The handbook says the method applies to all vehicle types at any speed. This is handbook guidance alongside the Highway Code's one-car-length rule (SPF, Basic Theory of Driving, para. 136).
The handbook separately says to watch the brake lights of the vehicle immediately ahead and traffic in front of it (SPF, Basic Theory of Driving, para. 137).
For motorcycle riders, SPF's current Riding Theory Booklet says to increase the following distance to 6 seconds (previously 4 seconds) when being tailgated or when the driver ahead is tailgating another vehicle. The current Basic Theory handbook also says the six-second rule may be used when riding with a pillion or extra load, or in adverse conditions such as a wet, slippery road or poor visibility (SPF, Riding Theory Booklet, paras. 125 and 244; SPF, Basic Theory of Driving, motorcycle following-distance guidance).
Stopping distance
The Highway Code says stopping distance consists of the distance travelled while the driver reacts and the vehicle's braking distance; it also says stopping distance varies with speed, reaction travel, and braking distance (SSO, Highway Code paras. 11 and 69).
SPF's Basic Theory handbook publishes this approximate stopping-distance chart. It says stopping distance is approximately reaction distance plus braking distance, and that both increase with vehicle speed. Distances are in metres (SPF, Basic Theory of Driving, para. 138):
| Speed (km/h) | Reaction distance (m) | Braking distance (m) | Approx. stopping distance (m) |
|---|---|---|---|
| 20 | 6 | 4 | 10 |
| 30 | 9 | 6 | 15 |
| 40 | 10 | 10 | 20 |
| 50 | 15 | 20 | 35 |
| 60 | 18 | 27 | 45 |
| 70 | 20 | 40 | 60 |
| 80 | 22 | 53 | 75 |
| 90 | 25 | 70 | 95 |
| 100 | 28 | 82 | 110 |
The handbook says braking distance also increases on a wet road, with worn tyre treads, or when the car is fully loaded; reaction time increases if a driver is tired or has consumed alcohol (SPF, Basic Theory of Driving handbook, p. 61).
Coverage debt
- The Highway Code does not set out a three-second timing test or a numerical stopping-distance table in rules 67–69. The three-second rule and approximate metre figures above are from SPF's Basic Theory of Driving handbook; its chart is not an exact stopping-distance guarantee for a particular vehicle or road condition.