J'ai oublié un truc : la priorité de droite, vous croyez que c'est un hasard ?

On donne la priorité à droite parce que l'on roule à droite, et l'on roule à droite parce que les droitiers étant plus nombreux il était plus risqué de croiser en étant à gauche

A savoir qu'étymologiquement le mot "droit" et "roi" on la même origine. Le roi étant celui qui a une conduite droite.

Ah bon ?
Donc en Angleterre, en Irlande, en Inde, en Australie, a Singapour, en Indonésie, en Afrique du Sud et au Japon, les droitiers ne sont pas les plus nombreux ?

Roi vient de "rex, regis" (d'où régicide, par exemple, pour la mort d'un des gauchers les plus célèbres !).
Droit peut venir de "rectus, a, um" étymologiquement associé à "rex, regis", qui est dans ce cas le mot signifiant tout droit (d'où rectitude, rectiligne).

Ce n'est pas le même droit que "dexter, era, erum", du côté droit.

To move in a straight line, with derivatives meaning “to direct in a straight line, lead, rule.” Oldest form *3re-, becoming *3reg- in centum languages.
Derivatives include right, realm, anorexia, rich, rule, interrogate, and reckless.
I. Basic form *reg-. 1. Suffixed form *reg-to-. right, from Old English riht, right, just, correct, straight, from Germanic *rehtaz. 2. realm, rectitude, recto, rector, rectum, rectus, regent, regime, regimen, regiment, region; address, adroit, alert, correct, direct, erect, incorrigible, porrect, rectangle, rectify, rectilinear, resurge, Risorgimento, sord, source, surge, from Latin regere, to lead straight, guide, rule (past participle rctus, hence adjective rctus, right, straight). 3. anorectic, anorexia, from Greek oregein, to stretch out, reach out for (with o- from oldest root form *3re-).
II. Lengthened-grade form *rg-, Indo-European word for a tribal king. 1a. bishopric, eldritch, from Old English rce, realm; b. Riksmål, from Old Norse rki, realm; c. Reich; Reichsmark, from Old High German rchi, realm; d. rich, from Old English rce, strong, powerful, and Old French riche, wealthy. a–d all from Germanic *rkja-, from Celtic suffixed form *rg-yo-. 2. real2, regal, regulus, reign, rial1, riyal, royal; regicide, regius professor, vicereine, viceroy, from Latin rx, king (royal and priestly title). 3. Suffixed form *rg-en-. raj, rajah, rani, rye2; maharajah, maharani, from Sanskrit rj, rjan-, king, rajah (feminine rjñ, queen, rani), and rjati, he rules.
III. Suffixed lengthened-grade form *rg-ol-. rail1, reglet, regular, regulate, rule, from Latin rgula, straight piece of wood, rod.
IV. O-grade form *rog-. 1. rake1, from Old English raca, racu, rake (implement with straight pieces of wood), from Germanic *rak. 2. rack1, from Middle Dutch rec, framework, from Germanic *rak-. 3. Possibly Germanic *rankaz (with nasal infix). rank2, from Old English ranc, straight, strong, hence haughty, overbearing. 4. reckon, from Old English gerecenian, to arrange in order, recount (ge-, collective prefix; see kom), from Germanic *rakinaz, ready, straightforward. 5. Suffixed form *rog--. rogation, rogatory; abrogate, arrogate, corvée, derogate, interrogate, prerogative, prorogue, subrogate, supererogate, from Latin rogre, to ask (< “stretch out the hand”). 6. Suffixed form *rog-o-. ergo, from Latin erg, therefore, in consequence of, perhaps contracted from a Latin phrase * rog, “from the direction of” ( < ex, out of; see eghs), from a possible Latin noun *rogus, “extension, direction.”
V. Lengthened o-grade form *rg-. 1. reck, from Old English rec(c)an, to pay attention to, take care (formally influenced by Old English reccan, to extend, stretch out, from Germanic *rakjan), from Germanic *rkjan. 2. reckless, from Old English rcelas, careless (-las, lacking; see leu-), from Germanic rkja-.
VI. Suffixed zero-grade form *g-yo-. raita, from Sanskrit jyati, he stretches out. (Pokorny 1. re- 854.)