(The question was asked here but the answers didn't really address what I am about to ask.) One rule about long vowels is that the long vowel for え段 is written え段 + い. For instance けいじどうしゃ is pronounced as ケージドーシャ, not ke-i-ji-do-u-sha.
What about the ている pattern for verbs, as in 知っている? Is it te-i-ru or te-e-ru?
The rule you mentioned does not apply across word boundaries. For example, 海外へ行きます is pronounced like 海外エイキマス, not like 海外エーキマス, because へ is a particle and 行く is a verb. Likewise, 知っている is made of three words (知っ + て + いる, where this て is a particle), so it's not pronounced like シッテール. In addition, in colloquial speech, 知っている can be safely shortened to 知ってる, so there is no point of elongating て.
(Compound nouns like ため息 and さざれ石 tend to be pronounced like タメイキ and サザレイシ, too, but some people may pronounce them like タメーキ and サザレーシ.)
Your けいじどうしゃ example is right, but this one is definitely te-i-ru. I have never heard of anyone pronouncing te-e-ru, unless there's a part of Japan with rare dialect that I never been to.
