Timing gate, beambreak, tripwire

Trying to design transmitters/receivers for a long-range timing gate (across a wide road).
Test setup works reliably over a distance of more than 60 meters in broad daylight,
with ~120mA peak LED current (60mA current draw from a single LiPo cell).
Continuous modulated IR (no time gaps), and no optics (for a narrow ⌀ 5mm beam).

Writing some laptime test code for it (running on an Uno), and want to know if I made (interrupt) thinking errors.
Ignore the fact that a long time 1/1000 sec display is not possible with a ceramic resonator clock.
Just testing the principle here.
Reaction time should be ~1/2000 sec with a TSSP4038 receiver.
It still registers if I flick a ⌀10mm stick as fast as I can through the beam.

// Beambreak Sensor
const byte sensorPin = 2; // 3-pin TSSP40xx IR sensor connected to pin 2, interrupt 0
const byte buzzerPin = 11; // active buzzer, to monitor IR beam
volatile unsigned long currentMillis, lastTrigger, timeout = 3000; // lockout time after a trigger
unsigned long allSeconds, previousMillis, lapTime;
unsigned int pointer, runHours, secsRemaining, runMinutes, runSeconds, runThousands;
volatile boolean printed; // print flag
char buf[33]; // holds print string

void setup() {
  Serial.begin(115200); // set serial monitor to this baudrate
  Serial.print(F("BeamBreak Sensor\ntimeout set to "));
  Serial.print(timeout / 1000); // in seconds
  Serial.println(F(" seconds\n"));
  pinMode(buzzerPin, OUTPUT);
  pinMode(sensorPin, INPUT_PULLUP); // aditional pull up
  attachInterrupt(digitalPinToInterrupt(sensorPin), beamBreak, RISING);

void beamBreak() { // interrupt
  currentMillis = millis(); // trigger time
  if (currentMillis - lastTrigger > timeout) { // if valid
    lastTrigger = currentMillis; // update
    printed = false; // enable printing
  } else lastTrigger = currentMillis; // false trigger(s), new timeout

void loop() {
  digitalWrite(buzzerPin, digitalRead(sensorPin)); // buzzer follows sensor
  if (!printed) { // if not printed
    lapTime = currentMillis - previousMillis; // calculate lap time
    previousMillis = currentMillis; // set new start time
    allSeconds = lapTime / 1000; // calculate,
    runHours = allSeconds / 3600; // and print lap time
    secsRemaining = allSeconds % 3600;
    runMinutes = secsRemaining / 60;
    runSeconds = secsRemaining % 60;
    runThousands = lapTime % 1000; // last three digits
    sprintf(buf, "Event#%04d\tRuntime: %02d:%02d:%02d.%03d", pointer, runHours, runMinutes, runSeconds, runThousands);
    Serial.println(buf); // print the above string
    printed = true; // print once
    pointer++; // event pointer +1
    if (pointer > 9999) pointer = 0; // limit to 10000 events

In your beambreak when does “timeout” get defined?

Timeout is a fixed time that triggers are ignored after the first trigger (line 4, timeout = 3000 milliseconds).
Should stop multiple triggers, e.g from two wheels, or spokes, or two legs/arms.

Found an error in the lap time calculation (updated).

Can test the sketch with a button between pin2 and ground.
Triggers when the button is released.