Therefore, in spite of strong opposition by the car companies and people's egoistic interests, car traffic should be gradually reduced and eventually prohibited.

strong 的意思是"强烈的"，表示程度很高或力量很大。 opposition 是名词，来自动词 oppose（反对），加上名词后缀 -tion 构成，指"反对、对抗"的行为或态度。 strong opposition 表示"强烈的反对"，指反对的力度很大。